2003 Cadillac Seville STS Misfire I cannot solve:(

Hello! I have a 2003 Cadillac Seville STS with 133k miles on it. I recently bought it from an old couple who took great care of it. The interior and exterior look amazing and I just love the look of this car. I know all the problems and crap the Northstar is famous for, yet this is my second one and up until now ive never had a major problem I cant solve on it. So here is how it started... I bought the car knowing it had the common intake plenum boot rip in the bottom as it sounded like it was cammed at idle lol. Before I fixed this i replaced the plugs with denso double plats but I unfortunately only did the front four and left the rear autolites in there. I drove it for two days like that before i replaced the back. Thats when my P0300 check engine light came on. P0300 is the only code i have for powertrain. Other than that i just have a few annoying codes like for my radio and drivers seat. Anyways here is all i have done so far..oh very important info. ONLY MISSES WHEN COLD. Cylinder 7 and 3 seen on my Autel MK908. Pretty sure 3 is a fake mis as it is right after 7 in the firing order. Once it warms up the miss is gone. I can do WOT all day and it pulls hard with no hiccups all day.
Replaced all 8 Spark plugs with Denso double platinums
Replaced intake manifold gaskets and intake plenum boot that was ripped (Solved rough idle but miss is still the same)
Replaced fuel injector orings and swapped #7 injector to another cylinder which didnt do anything with the miss
Replaced rear Coil module and Ignition control module. Each bank of four has its own coil assembly with its own ICM
Compression test while cold- All 8 Cylinders are 30-40psi above Factory service manual spec (with 7 being the lowest but only by about 5psi)
Ohmed out the injector wires and ignition control module wires while moving the harness
fuel pressure test Key on engine off held 42psi for 20min then i disconnected
Vacuum test seemed steady at 17in think this was a warm motor though
Radiator combustion leak test and fluid never changed color
Ran it hard then took off rad cap to let pressure out to see if coolant was leaking into cylinder while sitting but it still misfired when cold again
sprayed everywhere cold and hot for a vacuum leak in my new intake manifold gaskets etc but got no change
Cleaned IACV, TB and MAF sensor. MAF was already very clean but did notice the honeycomb screen was slightly bent on a few "combs" not sure how bad that is or if it would affect anything.

PLEASE help I am stuck on this one big time Maybe i miss something i dont know. Im 21 and learning as I go but this is getting frustrating lol

Try a crankshaft variation relearn?? How bad is the misfire when it happens?? Also you may have to re Smoke the intake

One other thing you could put a pressure tester on the cooling system for an hr or so look down cylinder 7 hole see if coolant is getting in the cylinder

Swap spark plugs with cylinders 1 and 5 see if they move... could be defective plugs. Also ohm the plug wires and put on dielectric grease on the plug wire side of spark plug. Sometimes when pulling plug wires the core can get ripped out of terminal also not completely seated can do the same.

So actually the misfiring started after changing the plugs on the back bank or only the code p0300 then showed up and it already misfired before?

If the misfire started at this point I'd start there...may be the plug was dropped before. Can you scope (or know someonne who can) the ignition?

Hmm ..fuel trims and O2s?..it only misfires when cold? ..what are the readings in closed loop? ..can you insert a spark checker ? ..helped me to run down a bad coil pack ..as I could see the spark being slightly arrested when missing ..I know you said you ‘ohmed’ out the plug wires ..but ..wires are quirky ..try swapping ..being careful not to damage ..(unless of course you can get a new set) ..I’d like to know what the scanner is reading when it’s cold ..and then warmed up ..anyway ..good luck ..I’m curious too ..and will check back ..

I can feel shaking when it misses when cold. It’s weird it doesn’t hesitate or anything when I rev it but when I let off and the rpms drop I’ll feel a more violent shake then it gets back to idle and just shakes a bit. How do I do a crank variation relearn? It just started out of nowhere right when I bought it

Misfire started when I only changed the front 4 (opposite bank of misfire). I drive like that a couple days with 4 different plugs but same gap and double platinums. It’s weird it started missing on the bank I didn’t even touch yet like what the hell.... I also messed with the MAF and IACV that day too. But the MAF is super clean only thing I could see is the honeycomb screen has a couple small bends in it nothing major

Short terms are close to 0 at idle and my long terms are less than 5 I believe. I’ll have to recheck because it’s been a while. Coolant and IAT are within 5 degrees of eachother at startup. Scanner showed a pretty rich 9.5:1 ratio on startup that seemed very rich to me even for a cold start at 50 degrees. Think MAF was reading 2300hz at cold start high idle of like 1300 or something rpm

The crank sensor relearn is done with an appropriate scan tool.

Did you inspect the park plugs you had changed before?