Hi guys, as the title says my car is higly too high

Car specs
Te magna
3.0 liter v6
Auto

I just purchased this car, and down an engine swap with a spare engine that come with the car.
After getting the motor running the car seems to ideal to fast, was at 2000 rpm, but after running for about 10 mins revs have gone down to 1500-1600 rpm. I have replaced the oxygen sensor in the exhaust, the stepper idle motor. and changed the air flow meter.

One i put a timing light on the car the timing mark is like a quarter of a turn from were it should be. If i disconnect the air flow meter , then the timing jumps to top dead center and the revs drop to around 1000 rpm. The air flow meter is good as it come of a car that was running fast.

Any help would be appreciated , as this is a new experense for me to have a dizzy with no cogs to set the timing.

Thanks everbody

Have u tried the idle control screw on the side of the throttle body?

yes at the moment is backed right off, tried but does not decrees reves.

Dammmm not sure then sorry i'll leave this for someone else.

Thanks anyway

Air control valve or a vac leak, will be either one of these

Air control valve , sorry no idea, were would i find this and is there a way to check if it is good or bad. thanks