Tailpipe readings are kind of iffy to start with. A slight exhaust leak and your readings are shot.
However, headers will lean out a car just like any other mod that increases the engines ability to breathe. The PCM can only learn at light~moderate throttle, which it would then use to make assumptions about heavy~wide-open throttle. Either way, fueling can be off up to 8~10% with the stock parameters still in the PCM on a bolt-ons car. I would seriously think about investing in a tune, tuning software, or at least a MAF translator to help bring your AFR in line. Just make sure you get a better reading than from the tailpipe.
__________________ The best LS1 tuning software, period. - The preceding statement is solely a matter of opinion as expressed by a non-EFI Live affiliated individual with over half a decade of experience tuning LS1 equipped vehicles. It is in no manner an attempt to discredit, bash, or dishonor the alternative products offered by EFI Live competitors. Individuals interested in purchasing a tuning software package are highly encouraged to form their own damn opinions.
Last edited by SSpdDmon; 02-22-2007 at 09:07 AM..