1997 Chevy Silverado Z71 350 5.7L V8 K&N drop in. Magnaflow cats. Flowmaster catback. Getting about 11 MPG at 7200' Best I've ever got was 16.6 purely highway. Recent full tune up. Wires, plugs, cap, rotor, fuel filter. When I went to change the cap I noticed where the screw would go in is cracked. It doesn't hold the cap down very well at all. So I guess my question is, is this what could be causing this random misfire at high RPMs? It doesn't happen all the time, but sometimes when I go to get on the freeway and floor it, it will pop up when I'm in the higher RPMs. The CEL comes on when it happens, then a few days later it'll turn off. So it's not a huge deal. I would just like to get it fixed, whatever it is. Any other ideas on what could be causing this? If you need me to clarify anything or go into depth on something just let me know. Thanks! - - - Updated - - - Morning bump!