Ok well i just had some lt's and OR x pipe put on a few weeks ago. When i get over 4000rpm, the check engine light comes on, but once i drop to 2000 it goes away. i have a feeling this may be due to the new location of the O2 sensors? Havent noticed any problems, but its still makes me a little uneasy.... anything else it could be, or how can i fix it? It seems to come on at even lower rpms now since i installed my 76mm maf w/true flow intake, and 70mm tb and spacer. Oh and i installed UD pullies, ac delete, new water pump and 180* tstat, and removed all smog stuff at the same time. I don't think its anything serious but it still bothers me to see a CEL at high rpms!