i dont think the o2 sims are your problem i think you have a spark plug wire problem or some other problem to get the misfire the o2 sims would just give you a constant ses light when it flashes it means you have serious problems and should only let you go about 65 and then flatten out you could not go any faster.

 

Can you pull the sim's out and replace them with the old 02's to verify if they're definitely the problem?

You didn't mix up the 02's right? (They are different front to rear.)

FWIW, I've been running these headers in my truck for a few months now - I haven't thrown a single code or had a high idle or anything, even in this single digit weather we have now.

 

Well I checked the plugs & wires but couldn't find anything. The only misfire that occured is right after I washed my engine thats when the ses light flashed. The plugs are new,I just instaled them on sat night. As far as 65,I can go faster than it just falls on it's face after 75mph or when it shifts into 3rd gear. Could this be any of problem? I have washed my engine many times before and never encountered this problem before. I guess theres a first time for everything!!!!!! Thank you 4 your input.

 

I put the old o2's back in to go to the dealership so I cuold get the codes. After getting the codes,my buddy cleared the computer and on the way home,the ses came on again. So with that being said,I'm sure that if I went down to the dealership again,the misfire probably wouldn't be on there. No I didn't mix the o2's up but after the install,I started the truck and right off the bat,the truck started to idle very high(1300-1800rpm's).

 

Well I fixed my misfire prob,my #1 plug wire was off for some reason. Runs good now!!

 

Shoot... glad it's fixed!