XJ surging problem

just replaced the head gasket on my girlfriends 92 4.0 HO xj. everything worked out pretty well except when we went to drive it. we drove down the road about 1/2 mile turned around and got it up to 55-60 and the jeep started bucking and surging really bad, but the rpms stayed constant, so im sure that the engine wasn't the problem. I checked the tranny fluid, and i must have overfilled it, cuz it was past the squiggle in the tranny dipstick. I went to autozone and the guy there said check vacuum leaks, compression, and plugs...anything else? anybody got any ideas?

Zack

clean your throttle body, it is the cause of many problems.

already have...its pretty clean.

Zack

Have you checked your TPS?

after searching on here and other sites, ill check it...how can you test it? voltmeter?

Zack