Ranger issues after headgasket replacement

Hey there, I recently helped my girlfriend put new heads and gaskets on her 2000 3.0 flex fuel ranger, and I got it started up and and everything worked good except for a popping noise coming out of the exhaust. I'm no expert on this stuff, but I would assume it is a misfire or backfire. When the popping sound happens it shoots exhaust out in a hard puff that I could feel with my hand that is significantly stronger than the regular exhaust coming out.

It has brand new spark plugs and all the wires are properly allocated, and the idle air control valve and mass airflow sensor were both swapped out and didn't fix anything. The popping occurs a lot, but it's not completely constant and when I rev it the interval of the popping noise goes way down and almost stops. With that said I don't think it could be a timing issue (especially since I never messed with the timing) and I don't think it could be a spark plug/ distributor issue because I would think that revving it would make the problem worse.

The truck has the CEL on and has 3 codes: p1150, p1151, and p0174.

Any theories as to what could be causing this would be appreciated!

All of those codes are intertwined indicating a lean condition. I'd start by looking at your o2 sensors.

If those check out then you may have more issues on your hands in the case that something may have went wrong with the repair.

Just checked the fuel pressure with a gauge and it's at 10 psi when I think it's supposed to be 55 PSI. That would explain the system too lean codes. Do you think that could be causing the mis/backfires?

Lean misfires are a thing and can be caused by low fuel pressure amongst other things.