the only things i know of for that car would be to clean the carb (which you said you did) and check the vaccum hoses for leaks. i would imagine it wouldnt hurt to change the filters and spark plugs and wires if that hasn't been done in a while.

theres probably more you can do to narrow it down some, but someone other than me will need to point you in the right direction

EDIT: just browsing the forums for you and found some comments from people suggesting to also check for a faulty idle air control (IAC) valve and/or exhaust gas recycling (EGR) valve that may be sticking open (does this car have these?)