Hey dude, i think i know what is your problem, well at least take it as an advice.. I had the same trouble not long ago, I have a 1994 accord coupe manual trans.. As soon as the engine got a little warm, while going from standstill to foward or reverse, of just being in 1st and really slow speed (0-5km/h and the car going back and forth cuz of old engine mounts) I heard a CLUNK noise from under.. i tought of something banging, like engine on something, loose trans pieces or somethig.. Well i found my answer while looking under my car on a lift at school..! *The catalyser support is your problem* If you can get under the car try to look at it if its rusted where it meets with the cat, and try prying it *gently* (i broke mine off..damn!) You may hear that clunk noise.. Its due to the heat making the metal dilate and then it does the shit.. I even have the exhaust buzz problem at 1800rpm but thats another story! Hope i could help you out! tell me about it