More problems running

I figured I would start a new thread about the problems with my combo. I rewired the grounds on the EPEC and MSD, directly to the battery. I put new AR3924 plugs in gapped at .028 along with a new cap and rotor. The engine runs fine for a while at part throttle, low rpms. It does stutter a bit from time to time and you can hear it popping in the exhaust occasionally. At part throttle, A/F is around 14:1-15:1. The O2 reading bounces around a bit when you can hear it popping in the exhaust. After driving for about 30 minutes this morning, I got to a place where I could do a WOT pull. At about 4800rpm, the tach starts bouncing around and it is like I hit a wall. The rev limits in the EPEC are set well above that rpm. I data logged this run and everything looked to be working okay from the fuel/timing perspective. Any ideas what it could be? My first thought is a bad TFI as the part throttle problems seem to get worse after driving for a while and so, hotter underhood temps. I just don't want to start throwing parts at it. Thanks for any input.