98-00 4.3 PCM tuning advice needed.

[12sws27]

I have a 98 GMC Jimmy 4.3L 2wd auto. Right now I'm running 6psi with a S/C.

With my stock fuel system the IDCs were at 127% at times. So I sought a means for more fuel since the stock system was not upgradeble.

I found that many use a mercruser 4.3 marine intake. So I put one on.

The marine intake (MI) came with 24lb/hr@3bar injectors. I played around with those for awhile but never felt confident about the tune since I had no luck what so ever finding info on those injectors. IDC with those got up to 90% so I figured since I had 39lb Cobra injectors and plan on more power I'd swap them in. Plus info on those could be found.

I need someone to look at my logs and tunes and point me in the right direction here. I'm a bit confused. When I enter in the info that is supposedly the right info, my LTFT peg at 25%...

I'm attaching 2 tunes and logs. 1 is with what I understand is the right inj info and the other info I got from looking at other files of guys running the same injectors and used some of their info they entered.

I've tried differnt flow rates with both sets of injector info and the inj info in the "1st 39 blue giant" tune seems to always work better then the "2nd 39 blue giant" tune.

My truck also goes real lean after start up. First start after sitting for hours is the worst. What's up with that?

Also attached is a stock tune. It not from my Jimmy but should be pretty close to what it was. I don't have my stock tune since my PCM was originally tuned for the S/C for a tuner that does mail order tunes for these S/C kits.

[Bandit gs]

Put it on a WB and tune it through the MAF. I have a few 4.3 tunes but i've yet to work on one yet so i can't tell you specifically how the injector tables work.

[12sws27]

Thanks for the reply. I just figured out to log AFR% Error with the standard interface.

I guess I'm just going to use the injector info that gets me the closest and move on.

Thanks again.