I have had my 89 rs for about 2 years now and it has recently started to pop back through the intake and I have no idea what it could be...
I cleaned and adjusted the IAC, replaced oxy, tps ,maf... any help?

 

The '87 2.8L Camaro I used to have developed this problem as well. The '87 would only backfire through the intake during warm-up. In that car's case, it was the Intake Air Temperature (IAT) sensor. After replacing that sensor, the engine's behaviour returned to normal and has been that way since. I discovered that was the problem on my car by looking at sensor data from the ECM. The readings from the IAT were WAY off.

 

Thanks for the reply, It has taken me a while to repair the problem and you were right it was the IAT sensor and the reading from the ecm were way off I also found that I had a stuck EGR valve. After fixing all of that my car has run great since...

Again Thanks alot...