Hello all, well i've got my car so far (8v PF) that i am ready to go and get new papers for it, I had it on the tester and all was good managed to get the co to around 1 percent and all seemed to be running fine. on the day i drove it to the testing station without any trouble, but after they took it inside it started playing up and misfiring, co2 way too high ( they call it Hc i think which is basically unburnt fuel i geuss) so i took it home and put it back on the tester and i cannot work out what the problem is, this car has had everything new, i'll write a list; plugs, leads, cap, 2nd dizzy to prove the first isn't bad, new icv valve,blue sensor (pattern), new injectors, new FPR, 2nd maf as was suspect on the original, new knock sensor, new Earths all around, new lambda, new Catylasator, umpteen different ecu's! I am at a loss when i had the motor out i reground the valves in and new head gasket e.t.c , i think i'll do a compression test on it next although i just removed all the valves and they do look all equally sooty none wahed clean or anything, can running rich cause a misfire, our machine at work is brand new and maybe it has a problem!!(clutching at straws). if anyone can point me to what should look at next would be great. just as an extra thought would the knock sensor cause problems as when i unplug it it doesn't seem to make a difference. sorry for the long post.