On a 87 Gt for timing you should unplug that plug on the side of the distributor and time it TDC and when you plug it back in it should advance 10 degree's, right????????? The reason I am asking is because I having a slight surge when I punch it either from dead stop, or about cruising speed in 3rd it sometimes backfire's {just a little} I HAVE A AOD Tranny. also if I floor it when I get to third gear if I let off just a cooder hair's worth it jump's down a gear tries to anyway. I just recently added a BBk TB and trickflow Manifold Kit everything is tip top TPS voltage and So on Idle's fine .