My camaro idles fine around town going at the most 25mph and can sit forever without having any troubles. When I get on the highway or freeway going about 60-70mph runs fine until I get off the ramp and slow down then the idle get rough and goes below 500 on idle and jumps up and down which makes it almost stall. What could this be? I can say almost every relay,distrubitor,maf,iac have been replaced all wire harness have been checked out or replaced. Need help... Anyone?

 

perhaps a sticking egr valve!

 

thanks for the reply but it was replaced too...