ive got a 95 vx hatch with the d15z1 economy vtec engine...it idles fine when its cold but once you drive a few miles and let it idles it sputters and tries to cut off, if you cruise at a steady speed it bucks and sputters until you accelerate then it doesnt do it. ive replaced the iat sensor iac plugs wires cap and rotor. it holds good fuel pressure of about 45 psi. any ideas of what it could be?

 

Along with the IAC did you check this:
https://honda-tech.com/forums/acura-integra-6/%2A%2A%2A-how-%2A%2A%2A-clean-your-fitv-aka-fast-idle-thermo-valve-1564019/
(FITV)
It could be your issue.