Update on my car!Power still missing.

Ok guys..

Fixed that exhaust leak from my headers, New KC clutch, 3.73 gears with some diff upgrades, and changed rear main seal!. Now the questions , My car sounds 100% better than when I had the leak (sounds like a mustang now), I'm not so happy with the gears though!, I don't feel much of a difference, did'nt really test it out to the max yet because I wanna break in the clutch and gears properly. I also ditched my bosh spark plugs and went back to Motorsport's (ford recomendations), I just need to swap the wires and ditributer cap for some ford racing ones. My compression was at 125psi to 115psi.

Now I'm still missing some power!! What can I do next to see what the problem is?..I know when I took out mu h-pipe It was BLACK inside, If I buy an adjustable fuel thingy, and make it run less lean. Can this cause lose of power??...Thanks guys!