To put it simply I have had high rpm power loss issues and I finally got a new tune as I had a Madz28/Madtuner tune and I had Solomon at LT1tuning.com look at the tune and he said the tables looked funny and it could certainly benefit from his tweaking. So I got his tune and the car runs quite a bit smoother now and I also thought I had a valve float issue so I got a stronger ser of Lunati double springs from LE.

Now the car drops power a little over 6k where it used to drop power at 5700-5800 so the springs helped (I didn't have the new tune when I got the new springs so the tune only helped the car run smoother and didn't cause the high rpm power loss). One thing I noticed while datalogging and pushing the car to 6500rpms is that the MAP readings start to fall and the MAF reading stops climbing and starts bouncing around at 6k.

5,749rpms-MAF reads 316.80g/s
5,817rpms-325.89g/s
6,019rpms-335.97g/s
6,056rpms-314.15g/s
6,081rpms-325.89g/s
6,342rpms-339.98g/s
6,370rpms-319.92g/s
6,525rpms-331.88g/s

During this the KPA is hovering between 93-96kpa. Baro is 103kpa.

Anyone have any theories? Solomon says the intake seems to have a restriction or the valves could not be set right (Valves were set to 0 lash then turned 1/8 to 1/4 of a turn). Right now I have a B-body elbow that attaches to the 3.5" MAF then the K&N filter is directly on the MAF.
I'm currently converting to the factory style "straight" air intake the L98/LT1 Corvettes used with smooth bellows and an SLP Claw intake to try to help airflow. Then I can datalog again but does it seem to be hitting a glass ceiling of airflow based on the MAF readings? Is this a good indication of a restriction in the air intake? I'm looking for ideas here.

 

Could that MAF reading show that the heads connot flow anymore air? Or not because the KPA is dropping and showing something is resticting airflow? If the airflow is the issue won't the car lean out? (The injector pulsewidth starts to drop a little bit as I pass 5800rpms)

These are the specs I got with my heads (Never had them flow tested myself but they certainly looked the part when I installed them)

Lift: Int / Exh:
.200 = 134/104
.300 = 190/144
.400 = 235/172
.500 = 257/191
.550 = 265/195
.600 = 265/200

 

Also how much could a maladjusted valve hurt top end performance? Like I said before I adjusted them 1/8-1/4 turn past 0 lash.

 

Have you ruled out ignition issues? Knock retard?
Those erratic MAF readings usually mean either valve float, ignition breakup, or knock retard. Although knock retard (with stock tune parameters) usually decays more gradually than you're seeing.
MAP vs BARO looks like an intake restriction.

 

The Opti doesn't show signs of issues anywhere else in the rpm range but I'm not sure how to confirm it's ok at high rpm. No timing retard according to the datalog. The valve springs are brand new. No codes.

Also coil and ignition module are fairly new.

 

I have a theory that I have lifter issues. When i changed the valve springs most of the lifters were bled down after only sitting for a day. Also when I first set all of the valves I had to re-adjust 4 rockers as the car would not idle. Also 2 of the cylinders I couldn't get the clacking gone completely. Very very quiet clacking. Most people wouldn't hear it but I do. I ordered a new set of lifters and I'm in the process of replacing my whole air intake system. So after I get all of these things done I will report back.