After debugging for a few hours, the algorithm seems to be working. Right now to check if it works i'm checking the end node position to the currentNode position when the while loop quits. So far the values look correct. The problem is, the farther I get from the NPC, who is current stationary, the worse the performance gets. It gets to a point where the game is unplayable less than 10 fps. My current PathGraph is 2500 nodes, which I believe is pretty small, right? Any ideas on how to improve performance?

struct Node
{
bool walkable;      //Whether this node is blocked or open
vect2 position;     //The tile's position on the map in pixels
int xIndex, yIndex; //The index values of the tile in the array
Node*[4] connections; //An array of pointers to nodes this current node connects to
Node* parent;
int gScore;
int hScore;
int fScore;
}


class AStar
{
private:
SList!Node openList;
SList!Node closedList;  

//Node*[4] connections;     //The connections of the current node;

Node currentNode;           //The current node being processed

Node[] Path;        //The path found;

const int connectionCost = 10;

Node start, end;

//////////////////////////////////////////////////////////

void AddToList(ref SList!Node list, ref Node node )
{
    list.insert( node );
}

void RemoveFrom(ref SList!Node list, ref Node node )
{
    foreach( elem; list )
    {
        if( node.xIndex == elem.xIndex && node.yIndex == elem.yIndex )
        {
            auto a = find( list[] , elem );
            list.linearRemove( take(a, 1 ) );
        }
    }
}


bool IsInList( SList!Node list, ref Node node )
{
    foreach( elem; list )
    {
        if( node.xIndex == elem.xIndex && node.yIndex == elem.yIndex )
            return true;
    }

    return false;
}

void ClearList( SList!Node list )
{
    list.clear;
}

void SetParentNode( ref Node parent, ref Node child )
{
    child.parent = &parent;
}

void SetStartAndEndNode( vect2 vStart, vect2 vEnd, Node[] PathGraph )
{
    int startXIndex, startYIndex;
    int endXIndex, endYIndex;

    startXIndex = cast(int)( vStart.x / 32 );
    startYIndex = cast(int)( vStart.y / 32 );

    endXIndex = cast(int)( vEnd.x / 32 );
    endYIndex = cast(int)( vEnd.y / 32 );

    foreach( node; PathGraph )
    {
        if( node.xIndex == startXIndex && node.yIndex == startYIndex )
        {
            start = node;
        }
        if( node.xIndex == endXIndex && node.yIndex == endYIndex )
        {
            end = node;
        }
    }
}

void SetStartScores( ref Node start )
{
    start.gScore = 0;

    start.hScore = CalculateHScore( start, end );

    start.fScore = CalculateFScore( start );

}

Node GetLowestFScore()
{
    Node lowest;

    lowest.fScore = 10000;

    foreach( elem; openList )
    {
        if( elem.fScore < lowest.fScore )
            lowest = elem;
    }

    return lowest;
}

//This function current sets the program into an infinite loop
//I still need to debug to figure out why the parent nodes aren't correct
void GeneratePath()
{
    while( currentNode.position != start.position )
    {
        Path ~= currentNode;
        currentNode = *currentNode.parent;
    }
}

void ReversePath()
{
    Node[] temp;
    for(int i = Path.length - 1; i >= 0; i-- )
    {
        temp ~= Path[i];
    }
    Path = temp.dup;
}

public:
//@FIXME It seems to find the path, but now performance is terrible
void FindPath( vect2 vStart, vect2 vEnd, Node[] PathGraph )
{
    openList.clear;
    closedList.clear;

    SetStartAndEndNode( vStart, vEnd, PathGraph );
    SetStartScores( start );
    AddToList( openList, start );

    while( currentNode.position != end.position )
    {
        currentNode = GetLowestFScore();

        if( currentNode.position == end.position )
            break;
        else
        {
            RemoveFrom( openList, currentNode );
            AddToList( closedList, currentNode );

            for( int i = 0; i < currentNode.connections.length; i++ )
            {
                if( currentNode.connections[i] is null )
                    continue;
                else
                {
                    if( IsInList( closedList, *currentNode.connections[i] ) 
                       && currentNode.gScore < currentNode.connections[i].gScore )
                    {
                        currentNode.connections[i].gScore = currentNode.gScore + connectionCost;
                        currentNode.connections[i].hScore = abs( currentNode.connections[i].xIndex - end.xIndex ) 
                            + abs( currentNode.connections[i].yIndex - end.yIndex );
                        currentNode.connections[i].fScore = currentNode.connections[i].gScore + currentNode.connections[i].hScore;
                        currentNode.connections[i].parent = &currentNode;
                    }
                    else if( IsInList( openList, *currentNode.connections[i] ) 
                            && currentNode.gScore < currentNode.connections[i].gScore )
                    {
                        currentNode.connections[i].gScore = currentNode.gScore + connectionCost;
                        currentNode.connections[i].hScore = abs( currentNode.connections[i].xIndex - end.xIndex ) 
                            + abs( currentNode.connections[i].yIndex - end.yIndex );
                        currentNode.connections[i].fScore = currentNode.connections[i].gScore + currentNode.connections[i].hScore;
                        currentNode.connections[i].parent = &currentNode;
                    }
                    else
                    {

                        currentNode.connections[i].gScore = currentNode.gScore + connectionCost;
                        currentNode.connections[i].hScore = abs( currentNode.connections[i].xIndex - end.xIndex ) 
                            + abs( currentNode.connections[i].yIndex - end.yIndex );
                        currentNode.connections[i].fScore = currentNode.connections[i].gScore + currentNode.connections[i].hScore;
                        currentNode.connections[i].parent = &currentNode;
                        AddToList( openList, *currentNode.connections[i] );
                    }
                }   
            }
        }
    }

    writeln( "Current Node Position: ", currentNode.position );
    writeln( "End Node Position: ", end.position );

    if( currentNode.position == end.position )
    {
        writeln( "Current Node Parent: ", currentNode.parent );
       //GeneratePath();
       //ReversePath();
    }
}

Node[] GetPath()
{
    return Path;
}

}

This is my first attempt at A* so any help would be greatly appreciated.