I was told at the tailpipe was only 1 or 2 tenths difference. I also have a Needswings dual CAI and supercooler. I found 2 dyno pulls and the average was 11.6 with a maximum of 11.9 during the pulls. I've heard of lots of people going lean with a pulley, but for some reason I'm still rich. For any one that changes a pulley, check it on a dyno.

Les

your being rich is good. don't want to be lean. sounds like your A/F is dialed in pretty good

13.1 is quite lean. That's fine with a stock tune and stock boost. However, how much do you really trust your tuner? Mercedes spends a lot of time and money on R&D making sure the tune is good for every condition (temp, humidity, altitude, etc). For an aftermarket tune, I would want to see AFR's of 11.5-12.0 on a warm day. I cringe when I see 12.5 on a tuned motor. Most tuners will tune to 11.5-11.8. I would prefer to lose some power/fuel economy, be safe rather than gain some power and blow a motor due to detonation. Anyone with this "Jerry Tune" log any AFR data? BTW, I've run water/meth injection on all my previous F/I cars. However, I haven't found a good way to tap the rubber intake hose for the nozzle yet. I always run a water/meth kit for added safety.

Also, I've tapped the exhaust tailpipe before to measure AFR's, I find it a very inaccurate way to measure AFR's on the dyno. I installed a AEM UGO wideband AFR on my volvo a while back and the tailpipe readings were inconsistent. It was never +1/-1, always fluctuating. I honestly would not rely on that as a way to log AFR data.

Bryan

Why does everyone say tune before heat exchanger? I would think tune would be the last thing you do so that the tunes includes all your mods??

Re-tunes are free. However, I did my pulley and tune last so I'd have all the necessary cooling to make it efficient.

Oh ya I forgot they were fee....crap I really need to just tune my car then ASAP