Specifically intake valves I assume, so I'd rule out AFM as the cause.

 

Did you do a crank relearn after the engine replacement???

 

sure did!

 

Cam and crank installed dot to dot?
Did you happen to check fuel pressure.

Is this a 2007 NBS or NNBS truck. IF NNBS are you positive it's a 58X crank I really don't know how the pcm would respond with the older crank hell it may not even start if it was not a 58x crank.

 

......finish doing the compression test.

 

Are you sure its a backfire and not a misfire? Kind of sounds like wrong injectors/ injector data, but either way a fuel issue.

 

Only way I know is to swap it with a known good one. Did you do a VVT delete when you put fresh heads on it? If so, did you delete VVT from the ECM?

 

didnt touch the vvt, left everything stock.

did the crank sensor relearn

checked all the fuel injector pulses and they are good

double checked all grounds

exhaust not plugged

swapped #1 o2 sensors from left to right bank, no change

changed the bad bank 1 rear 02 sensor and its working now, no change, and now there are no trouble codes

the short term and long term fuel trims are all at 0% (not sure if this is normal)

put in new plugs

old and new engine were both 58x wheels

ordering new spark plug wires now even though i doubt thats the problem

drained old gas and put in fresh gas

map sensor is good

maf sensor is good

throttle body is good

coolant temp sensor is good

oil pressure sensor is good

all 4 02 sensors are reading correctly

coils are good

fuel pressure is good and steady. Will fluctuate a small amount when struggling to idle

did compression test on all cylinders except #8 because it was hard to get to. All are 210 on the dot

 

Use a scan tool to determine if you are getting missfires and if so which cylinder(s). Then you could pinpoint it at to valves, electric, etc.

 

ugh, cracked intake manifold