My b20v seems to running lean according to my AFR gauge after I changed the spark plugs. I didn't think it would cause an issue the old plugs were paper bag brown so they car wasn't running lean and my AFR were in target range now it idles 16 but WOT is in the 12-13 range. Am I over thinking this or is there something I should check. Car is a b20z2 block with a b16a2 head stock tuned on a phearable ECU and car has held a good tune for the past 3 years

 

As long as the wide-open-throttle A/F is like 13.2 or LESS (as in smaller number - richer), then you are good. 16:1 at idle is a bit lean, however, it isn't going to hurt anything... so as long as the engine doesn't stall at idle or under deceleration, you should be fine. IF the car pops/stumbles at idle to part/mid throttle, this would suggest that the engine is running a bit lean from these locations in the fuel table, so if you want things perfect again, maybe a quick touch up tune with your tuner would be a good idea.

If you are only seeing 16:1 at idle or real light throttle, and then the engine A/F gets richer during mid rpm part throttle operation... say high 14's down to high 13's... there is a chance that you have a slight exhaust leak that is introducing air into the exhaust system creating altered A/F readings.

 

Yeah everything seems fine under WOT and and deceleration car pulls strong and doesn't misfire or pop. I'll check to see if maybe wideband came loose and I'll check for leak in exhaust. I don't tune so I'm hoping I can find the issue by myself