My baby has a problem

[stewdogg]

2004 1500FI
1,450 miles

So I spent the day Saturday taking off my stock exhaust and installing my new V&H exhaust, speakers, tail light wiring, rear fender, seats, and gas tank. I didn't get it all togethter until about 1:30am so instead of taking it for a full ride I just started it and reved the crap out of the new exhaust and everything sounded great. Today I went to take it for a ride and getting out of the driveway was fine all the way till I hit somewhere between 1/4 and 1/2 throttle and it falls apart and doesn't want to run.

...my stepdad started it for his buddy on Monday to hear the new rumble and ran it out of gas. Not knowing I only had enough gas in the tank to test for leaks and starting (1/4-1/2 gal.)
That is the only odd thing I can think of at the moment.
Although the fuel pump is working because you can drive it at 1/4 throttle and under just fine.
I didn't think that just changing the exhaust would cause this? It throttled out pretty good Saturday night (without being under load I do suppose) without any issues not even backfiring/popping after decel.?.

Thanks for any ideas!

I will have to update the sig pic real soon.