I have a 92 hatch with a 94 gsr swap and drag 3 kit. Lately I am having this very annoying problem that the Honda dealership and 2 other places have no idea whats up. The car runs perfect from a COLD start. If I shut the engine off and restart it this is when it acts up. Here is what is happening and it does this with or without the turbo kit on the car....

This happens at any rpm in any gear. Just trying to roll along at say 20 mph steady in 1st the car accelerates and then abruptly decelerates then surges back on and does this constantly while holding the throttle steady! This is crazy trying to go over speedbumps at school. In neutral I tried to hold it at a constant 2500 rpms and it goes to 2500 then to 2000 up to 3000 and just sits there and goes up and down between 2000 and 3000 rpms.

I took it to this other garage today and they checked it out. The guy said he wasnt sure but he says I have a "lazy" o2 sensor. He went on to say sometimes it is slow to respond and it even cuts out at times. Before I shell out $$ for a new sensor anyone have any ideas or know of anything I could check myself? Thanks in advance.