93 GT running odd

My 93 GT starts fine and idles smoothly. It has about 83,000 miles on it. Besides some Headers and a flowmaster exhaust, the engine is stock. The problem is, when I give it gas, the engine bogs down, pops, and hesitates very bad. I have gone over the ignition system replacing everything from plugs to the TFI module. Timing seems to be dead on at 10 before TDC. I have replaced the fuel filter and the fuel system reads from 35 to about 42 psi, which is about normal. I am running out of ideas and places to look. I have also gone over the vacuum lines and cant find anything disconected or a broken line. To get the engine to accelerate at all I have to baby the throttle and nurse it so the car doesnt start poping and stuttering. I am not getting any engine codes either. Please help!!! I am stuck on this problem and its driving me crazy!!

The problem seems to be progressing. It started as, maybe needed a tune up, and is now at the point where it seems to have a serious malfunction. After I time it and put the jumper back in the timiming does advance about 8 degrees. Also I am assuming 10 before TDC is the right timing, my emmissions stickers has been gone since I got it painted. Either way, I have retarded and advanced the timing but neither seem to help.

The condition improves slightly as the car warms up, however, it accelorates rough and the change isnt that much better. Ill check the TPS and see what I get from it. Thanks for the welcome and any other tips would be greatly appreciated.:SNSign: