2000 Nissan Altima, surges/hesitates off idle (post headgasket swap)

[RobZ71LM7]

I recently replaced the headgasket on a '00 Nissan Alstima KA24DE. The head was milled, new valve guide seals, pressure and vaccum test. I recently changed the plugs and did a compression test on all four cylinders and they came back fine. I also replaced the MAF sensor with a reman since the original was sometimes reading 24lb/min at idle. Ignition timing is 20* BTDC and the distributor rotor lines up at this setting where it was when I did the tear down. So valve timing appears to be on.

The car starts easily and idle fine, but will hesitate off idle sometimes and wants to cut out at 4K rpm.

Scanning it the only unusual thing I've noticed is the load value % is really high at idle like 30%+.

Any ideas?

[jwerty1]

tps, iacv, maf...assuming the headgasket job is ok

[RobZ71LM7]

Well I'm about to knock it out tomorrow. It's a combination of a plugged cat and a contaminated O2 sensor. the O2 cleared up a lot of it but it loses power up top and has a bunch of backpressure. I'm going to gut the cat tomorrow.