2006 STX12F surging idle.

[Homer]

After drowning my 12F a few months ago, I pulled the motor to make sure there was no contaminated oil left in the engine. Compression was a bit low, and I traced this to leaking exhaust valves. Piston rings gaps were spot on, as was piston and bore. So, engine got new intake and exhaust valves and seats recut. Engine is all back together, cleaned the throttle body and set the base idle screw at 3.5 turns out. Engine starts and revs fine, but surges badly at idle. (see video) Any idea what causes this??? Thanks in advance

[Myself]

Double check that you got the intake sealed back up. That really sounds like a vacuum leak surge.