First start after rebuild

[hfb1995]

2004 Mazda 3
2.3 hatchback
5 speed.

So this is what i did
I removed the engine due to rod knock/welded bearing

Did a complete rebuild
flywheel
clutch
Balance shaft delete kit
Cos-worth Crankshaft
Rods
bearings
head gasket set
seals etc
but i didn't change the oil pump ^^

when everything was said and done it started right up and ran really smooth and good, no leaks, no smoke from the exhaust.. everything just perfectuntil..

No need to read all of the above only for more info
My Problem is this..

When i start the car and leave it running everything is smooth works perfect,, it revs well and runs at idle 700-800

but asap when it hits operating temperature it runs almost like its firing the spark at the wrong time on one of the cylinders and it starts clunking and squealing a little too well i never let it running long enough to check it out i always turn off at that point...
and also when it hits operating temp i cant rev even when i rev it, it just starts stalling and running rougher.

No overheating
The oil pressure from a mechanical gauge is 80 psi on cold start and settles at 30 psi after it warms up....

what could this be?
I know i didn't change the oil pump as i was supposed to but the feeler gauge was within specs..

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