Keep us posted on this. Everything I know tells me that you should be pulling pretty damn hard up to 120, then slowly dropping off with your mods. It shouldn't be hard at all to hit 128.

Aha....the 3rd gear limiter in the 2000+ models.
Where you in 3rd gear. If so, it is limited to about 4000 rpm or 108 mph.
Once it shifts into 4th gear, you should be able to creep up to 128 mph.
Be careful because if you give it too much throttle it will downshift back to 3rd gear and the limiter will come back on.

Yea, I thougt about this but I was in D and started from 20mph and ran it straight up to 109 at WOT, hesitated around there, i figured it was the limiter so i let off and then floored it back down, crept up to 116 then started to float again just like at 109 almost like another limiter....

Well first thing first, the car is going to have trouble going over 110 because the 3rd gear "governor" is at 110mph. The car will not exceed 110mph unless it is in OD with the stock PCM, so you can't go WOT or it will try to downshift, so that is the reason you are having to lift and are not able to pull right to 128mph. Obviously a little PCM programming would fix that problem.

I can tell you right now what would get rid of your KR...it isn't an octane or plug problem at all. (Besides, I don't think you have to go lower than 1 range colder unless you are pretty modded, you just have to tune the car properly. We had 1.5 range colder plugs on the GTP until the day of the 12.4 run.) You are running too lean! (like you said) If you can get the 02 values up to 890 or 900 or so, the KR should go away, and I would bet your problem would be solved. But what you have to figure out is WHY the car is running that lean. Do you have a mini-afc or some other way to control your fuel? Also, what are you running for a thermostat? A 180?

Also, are you running WOT that whole time? I don't see a throttle position column, so I figured I would ask. (a hint for the future is to log throttle position, so you can tell when you were WOT so you make sure you aren't tuning for half throttle numbers.
It appears to me you let off right around the 66-67 area, is that correct?

Shawn

The scary thing is that you know that...I would imagine that the way you found out wasn't entirely legal.

Shawn

Well, here is the weird part. A few weeks ago when I dynoed, I had a mini-afc 2.0 plugged in at 100 (default no change setting) I was showing 02 settings in the 930 range and so was the dyno wideband 02 sensor. Both were right on and where they should be but i was still seeing the 2 to 3 degree knock at around 5200 in second gear. We tried to lean it out by dropping the afc to 98 percent with the anticipated leaning and actually got rid of the KR for the most part but actually lost HP. We richened it up to 102 percent and the KR was back and also lost HP. The best run was with the AFC at 100 default.

We figured that an AFC wouldnt help me and that the KR was actually false KR inputed by the PCM at that range. So these runs with no AFC attached show me running back in the 850 lean conditions. I am dynoing this Wed so we can see what its like with no AFC attached again. I'm pretty confused at this point. The car pulls SO strong now with the rockers right up to 110 and then boom, bounce even in overdrive so im guessing its another PCM thing here....

Well I am pretty sure you are right about at the point where the PCM can't keep up with the fueling, so you either have to run a mini-afc (or some adjustable fuel tool) or get your PCM reprogrammed. Our SSEi was running right where it should've been for fuel and everything until the rockers went in, then it just couldn't keep up and it was running right about where yours is. So we put on a mini-afc at 105%, and it killed 7 degrees of KR and REALLY woke the car up. So I would definately do some tweaking while on the dyno if at all possible.

Shawn

No comment. But I know where the devil lives, and I have danced with him. Turtle danced a little longer than I did No speed runs tonight. My front tires are running at 20psi right now.

Shawn, thanks for popping in here. You folks really know your 3800'*, and document well.

I think with the stock fuel system and new the rockers, you may be getting more air and not enough fuel? Did this ever occur before the new rockers?