More X-brand mysteries... this time my 04 cobra

Car ran fine for couple years with this setup, took crank pulley off over winter to rebuild and now is down on power with some surges of acceleration that 'almost' feels like it used to. I checked pulley alignment and found an offset between the crank and the other pulleys, corrected the pulley offset and it changed nothing. Brought it to a dyno for some pulls and also to verify the A/Fs on passenger side (my wideband is on drivers side) are still good.

Well the A/Fs are fine so thank god don't have a lean cylinder on my non-monitored side, but graphs say it all, low power and surging wildly. Below is graph and below that is datalog from SCT during the pass, wideband on dyno is passenger side pipe, wideband in SCT is drivers side.


Full symptoms:
-Low power overall except "sometimes"
-Airflow maybe slightly less? Hard to judge with the high temps we've been having
-Car idles lower and smoother, almost like there's more load on the engine
-Idle vacuum also lower, about 17.5 inches at 850ish (20ish normally, but also used to idle at like 900-950ish due to single blade TB)
-Idle vacuum does recover to 20 or slightly more with SC belt off
A/Fs at WOT are the same, short terms are right where they used to be

To date:

- I've run a compression test, all cylinders are decent, #1 is down by maybe 10ish psi
- We did a dyno pull with the cap off my catch can and blow-by was negligible
- Re-gapped my NGK TR6s to .028 from .032
- Swapped TR6s for brand new NGK BR7EF gapped at .028
- Swapped MSD coil pack set in the car for spare OEM set
- Swapped BACK to TR6s gapped all the way down to .022 to verify not a spark issue
- Re-aligned crank pulley as described earlier
- Had several different belts on it


0 changes from any of this. The car doesn't break up when it surges, it just feels like someones holding the brakes and letting off randomly, this only happens at WOT. Car runs great, runs as cool as usual, doesn't use a drop of coolant or push any out of the overflow.

Next things to do:
-Maybe refine crank pulley alignment as there is some angular mis-alignment between it and the SC
pulley
-Would like to pull valve covers and make sure no broken springs or popped off rocker arms...

Have you guys seen valve springs cause this issue? Or considering it's a 4 valve engine, maybe 1 rocker arm popped off or 1 broken valve spring cause this?