Help needed with Lean 4.6 2V. Logs enclosed

Here is a WOT 2nd gear datalog from my 01 mustang 4.6L 2V with return style fuel system that does the 1/4 mile in 15.9 sec at 92mph. Obviously, I am way down on power. At about 4800rpm the MAF flatlines and bank 1 goes lean all the way to redline. Bank 2 a/f seems fine. Any ideas? Fuel pressure never drops below 38psi. I have an idea, but I want to hear what the forum has to say before I skew the responses. No misfire codes. History of blown head gasket, and both head gaskets were replaced at the dealer.

Just got back from a 3 day event at NJMP with the BMW club. A lot of fun despite missing a few sessions to two cracked brake rotors... There was a Mach 1 there, and we ran south jersey parts stores out of rotors. Next time I'm bringing four spare front rotors!

I used the SCT to remove 2 degrees of base timing, and changed WOT a/f to 10% rich. That seemed to improve my power. I will do a log of this setup before changing anything else.

This week I will perform a compression test, and will swtich the plugs and coils bank to bank to eliminate them as a problem. After that, I may swap injectors bank to bank. The guys out in AZ at Bondurant think that its an intake manifold leak, and I should update to a newer plastic/aluminum intake.

MAF was clean, sprayed with solvent, and graphs did not change. Only the stock paper filter has been used. . Cats are almost new, high flow from jegs or summit.

My understanding is at WOT, computer is in closed loop mode.

I don't hear an exhaust leak. I don't know how an exhaust leak would cause a reduction in MAF readings.

I don't recall if I checked TPS, but I will. TPS would affect both banks I would think.

No oil burned, and I only run FLAT OUT!

Car has 9000 miles. I don't recall if we changed the O2's when we got the car 3000 miles ago. The O2 sensors seem to be working perfectly, since they I have done multiple WOT pulls, and the O2 sensor logs look the same.

My newest thought is that I'm losing spark on one of the bank 1 cylinders around 4000rpm. This is causing the engine to lose power, and sending extra oxygen to the bank 1 O2 sensor. That would explain a lot of things, and the computer would show 'lean' since there is uncombusted air that hasn't had it's oxygen used.

I have worked through the engine in the past couple of months. Ignition and spark were fine. Compression was good in all 8 cylinders too. Purchased a revised intake manifold and changed it out this week. That fixed the problem!

There was a chunk missing out of the gasket between upper intake plenum and intake manifold. The two gaskets from the intake manifold to the cylinder head appeared to be leaking as well. I don't have new logs, but the power is back. At the same time, I changed fuel injectors as well, but I'm pretty sure the problem was due to unmetered air, as expected.

Haven't done logs with the SCT, but I will likely take the car to JDM in November for a tune.