Couple questions

Could running too high an octane (92.5) in a stock computer'd SOHC ruin the o2 sensors or clog the cat? I put high octane gas in a week and a half ago cause I was going to try out the mopar computer, but the computer didnt work out so I started driving it again this week with the stock computer on the high octane gas, although I thinned it out with 87 as soon as I could.

Also, would code 21 cause the engine to "load up" and stumble, hesitate, backfire, when driving forshort periods at low RPMs, all the way up to 4000 RPM?

I ask because in the same time frame, ive been having a prob where the car will start to hesitate and run like crap at low RPM, like through parking lots, only for the problem to completely go away at exactly 4000 RPM every single time. I can steadily give it gas and stumble through the first 3950 or so, and right when I hit 4000 it hits and runs perfect. The only things I've changed in the last 2 months is the computer, which didnt work, and the gas.

 

how high of an octane did u use?

i know putting race fuel in ur car will blow ur cat, i dont know about the o2 sensors though........

 

it wasfumes of 87, what was left in the tank,8gal of 91, and 1 gal off 100 to get it up to 92, since we dont get 92 straight out of the pump, however the race gas was street legal unleaded vp race gas, with the mixture it averaged out to 92

code shows 21, but the problem is slowly getting worse

 

Check your plug wires!, mine would **** out on me up to 3,000 Rpm then after 3,000 she'd haul ***. then after new plugs problem fixed!.