Help with a Misfire!

[moneyshifter]

Ok guys, so I'm still in the works of figuring this out. just seeing if anyone can toss some ideas while i spend the weekend replacing parts.
i am running an m52 (2.8L) and it started misfiring a few days ago.
Codes:
STFT exceeds limits bank 1 & 2
02 Sensor heater circuit
random misfires cylinder 1 2 3 4 6 (nothing for 5)
So far i did a power balance test by unplugging the coils,
each cylinder drops RPM (200ish) except for cyl 5.
pulled plugs, they look fine but all other cylinders are running hotter than 5.
replaced all the plugs and swapped the coil pack & boot with cylinder 4 and cyl 5 STILL shows no contribution.

injector then right?
swapped the injector.... same symptoms as before.

i did verify the injector gets signal through a scan tool functionality test.
tonight I will be changing my 02 sensors but i doubt they will fix the issue. any ideas?

Side notes:
I bought this "project" 2 months ago and it has been running a "cut" T-Stat, one is in the mail right now but the motor struggles to reach operating temp. Oil shows no signs of blown HG, haven't done compression check however.

any questions or tips are appreciated!

[new318tifan]

You may have a vacuum leak somewhere.