Merc 8.1l 3200rpm max?
 

2006 Mercruiser 496
engine only revs to 3200 under load, additional throttle has no effect.

Mercury vesselview
Throwing a code for "TPS Sensor adapt A"
124-legacy
Swapped sensor, no change.
Unplugged sensor and it throws the standard "tps sensor" fault
anyone have any insight?

Ps. Ive already done plugs, coils, entire fuel module/pumps/filters, swapped ecm between engines with none solving my problem.

Does the ecm know that it's in gear?

I seen posts that say there's 2 different rev limiters. One for neutral and another for "in gear".

Rpm
 

Yes, if you rev up in nuetral it will rev all the way to the over rev engine alarm

Was it ok before then just started happening or did it start after some type of maint? Buy fuel from some new place?

Digital throttle ? Or cable controlled ?
If digital maybe in your dts throttle control unit

Engine was cutting in and out, it would start accelerating to 4000 buy the cut back to 3400, back and forth mostly randomly. Now it's pretty solid at 3200 Throttles are cables, other motor runs great so unlikely a gas problem as they share a tank

you have temp sensors in the exhaust.they have been known to go bad.