A 1991 5.0 with manual trans, 127,000, and bone stock besides header back exhaust and tune up. For some time now I haven't been able to rev above 4500 rpm, and when I do go that high it sounds like the engine hits a brick wall. After a good 15,000 miles of this problem I am ready to dive in and fix this. Here are some things that might help. When I play the radio, I get noise from the the plug wires, because the CD player part works without noise. I have checked and double check igintion timing and tried both advancing and retarding it. I have taken the TFI out and put it all back together with di-electric grease. New fuel pump, filter and I have constant fuel pressure. Cap, rotor, coil are new. No cats, so there not clogged, and the motor runs well beisdes this one problem. I thought maybe the I had valve float, a weak igintion or a faulty computer. ?????? any ideas ?????? I can't figure it out, non of my buddies have a clue.