1996 XJ Issues/O2 Sensor readings

OK I have the 96 XJ 4.0 that has the fuel regulator in the tank.It appears to be the only year the fuel sender can fit with the reg built in.I have been having running issues lately.I have my Snap On MT2500 hooked up,while driving down the road the front o2 sensor just sits at around .75-.72 volts indicating rich.It does work fine,new one installed checked it with an old sensor and does the same thing.I have looked at the magnaflow cat in there I installed new last year and it is completely clean,so that is not it.Swapped out ECM,Map semsor,TTPS and no avail to change the readings.Now mind you the header is slightly cracked,but the issue I have is mostly on the high way or accelerating it just falls on its face,with out down shifting until i push hard enough it down shifts.IF it was due to the crack it would show a lean running...under .45 volts.I have checked the fuel pressure only at idle..50 PSI and holds it for quite a long time.So has anybody had issues like this?I mostly want to fix the falling on face,slight surge when on throttle slightly slowing down.It got so bad one day that while on the highway with AC on up small hill I had the throttle down so much with out down shifting it completely pulled all the VAC out enough for the vents to blow out the floor.
It is a 4.6 stroker with 63mm t body and stock lift 2 wheel drive auto,neon injectors fuel trims are -3.0 to + 3.0 short term..like 5 to 6 longterm