engine rev prob

I know I am not giving much to go on here, but something is racking my brain about my car. I apologize in advance for a long post, but maybe some of this will help someone diagnose it...

It is a 2000 V6 with ~80K on it, 5 speed. The only things I have done to it is a K & N filter, homemade short-ram (actually a universal fitting pipe made for a honda from autozone), GT Takeoffs with a Pypes non-catted X-pipe. Nothing else significant engine or exhaust done to it.

I replaced the fuel filter a couple of months ago trying to solve my problem and just changed to motocraft regular copper plugs, and borg-warner (?) wires 2 weeks ago. Also, changed the oil a month or so ago with motocraft oil filter and full synthetic 5W30 oil made for high-mileage cars.

All that said, I cant figure out why my engine acts funky when i rev it up sitting still. I am not sure if I am hitting the rev-limiter or something or what, but I have 2 friends with v6 stangs and theirs doesnt act like mine. When I punch it sitting still, it sounds like its gonna roar, but then a second later it cuts down (not completely out), as if i was taking my foot off throttle completely. It does this in series of rev-cut-rev-cut a second or two at a time as long as I hold the pedal down. It doesnt act funky when im actually driving, even when I occasionally stomp it, just when i am sitting still...

I am sure it is something obvious here, but I can't put my finger on it. To my shame, I never really got into cars at all til i got my stang, and I still dont know beans about them . Hopefully this is something obvious and inexpensive to fix. If anyone can help me out, please jump in :)
 
When you are reving it up are you holding your foot on the floor? If you are then it's hitting the rev limiter. You're not supposed to hold it down, just a quick stab and release is all.