runs out of Revs

This has been the problem with my car since day 1, and I was curious as to your thoughts on the matter. My 91 GT is almost stock. It was treated to an H-pipe, flowmasters, and an air silencer removale before I got it. I added a few degrees of timing advance, and did a fresh tune up not to long ago. My previous mustang would rev to the redline with no problem, but this 91 GT seems to poop out at 4,300, and almost sounds like it hits a rev limiter. I can think of only a few things to do that could fix the problem: buy a new coil, take off those tiny headers, TFI swap or distributor issue.

I put in a new fuel pump and I got 35 lbs of pressure with no problems. I don't want to through a bunch of parts on without knowing what my problem is. I usually test this out in first gear, but in second it totally runs out of zroom too.

Any ideas would be so helpful, thanks, todd.

Ideas

No, just copper plugs, and I didn't have the regulator Vac. line off. I didn't know that it would do anything different. The mill has 120,000 miles and runs like a champ up to 4,000 rpm, and then it starts to run like an old milked out 4 cylinder. I have the stock rear end with the 2.73 gears, so I rarely go above 2,000 rpms anyway. I mean 80mph is about 1,500rpms. Just like to know what the deal is with this problem. I was thinking the coil is getting old and can't provide the spark it used too.

Thanks for any help. todd.