99 2.7l ignition timing off

So i have a 99 tacoma 2.7l 4x4 manual that has me completely stumped. But no one ever accused me of being the brightest. Anyways here’s the rundown


Symptoms:

Code p0505
Irregular and rough idle
Ignition timing is off around -8 at idle
Exhaust Backfires/ pops when you rev up and let off gas
Rattling sound from intake side
Swapped motor same exact issue
(Had a spare motor already)

Whats been replaced:

Coil packs
Wires
Plugs
Knock sensor
Camshaft sensor
Crankshaft sensor
Idle air control valve
Tps
Throttle body
Maf sensor
Motor swap
Grounds cleaned &tightened
fuel filter
Upstream o2
Vacuum hoses replaced and propane tested
Inspected wiring harness to best of ability


Notes

No cat, downstream o2 backed out of pipe to get proper reading (been like this for 6 months)

Possible issues?
Ecu
Wiring
Relay not inside either fuse box?

thank you in advance for any advice