Y2K1 SS 5.0 THIS

Alright, i'll start off by saying the mods so far... basically lid, SLP LTs, cutout/SLP Cat Back, MAFT, Adjustable Fuel pressure regulator. The problem im having is I am running SUPER lean under 2500 rpm where it finally flattens out. I got the car dyno tuned with the MAFT but we couldnt correct the low end lean, just got the mid and high end corrected. My current settings on the MAFT are +10% Base and -8% WOT, which I step to -6 or even -4 sometimes cause of the heat out here. I run my fuel pressure between 62-64 PSI (varies depending how much fuel is in the tank etc.) Anyways My question to all is could the higher fuel pressure be effecting the pulse width on the injectors and causing the car to lean out like that? I have a constant SES light on reporting lean codes on the 02s, and they are ALWAYS at 1000-1800 rpm. If I took the AFPR off and went to stock pressure would this correct my problem? I hate to spend more money tuning on the dyno if it wont help at all! Thanks!
BTW Here is the dyno graph with Air/Fuel
Dyno

LS1derfull

I dont see any reason you should be using adjustable FPR, put it back to stock and see the effect on tuning, you may have a exhaust or vacuum leak also to be lean at such low rpm, also verify you dont have a damaged 02 sensor.

Y2K1 SS 5.0 THIS

I wasnt worried so much about the codes, just the lean air/fuel down low that bugged me. I had the codes before I got the headers, pretty much since I bought the car. the AFPR got rid of some top end detonation I had before I got the MAFT, but I tuned the car with it in so I am scared I may mess up all the tuning if I remove it.

LS1derfull

Can you tell me your MAft. settings for each dyno pull on your graph?And did you Atap on dyno? What was your timing at?

Y2K1 SS 5.0 THIS

No atap on the dyno, the first pull was at Base 15% and WOT -2%, then went to -4 WOT, -6 WOT etc, after getting to -10% we dropped the Base to +10% and started at 0 WOT again, ended up getting the most power out of -8% WOT with little audiable knock. No one can explain the lean curve at the beginning though but I am starting to think the AFPR caused it
Edit - sorry I didnt make it very clear, That was my first and last pulls on there, first was +15% Base/ -2% WOT, last pull was +10% Base/ -8% WOT

<small>[ June 23, 2002, 02:06 PM: Message edited by: Y2K1 SS 5.0 THIS ]</small>