95 blazer runs great on the highway but wont idle for jack

My blazer has issues. It runs fine on the highway but when I stop and take it out of rear or am sitting at a red light it wants to die. It seems like a vacum problem but I checked for leaks real well and none show up. I pulled the plugs and gave it a compression check and they were all on 150 or 155 which is great for having 180k. All the plugs show normal wear. I tuned it recently altough I really dont feel its a ignition problem. The fuel filter is new the air filter is new. I cleaned the fuel injector and all that stuff. At first it was giving a egr fault so I changed the egr valve which was $120 and the check engine light went out for a while but it still ran like crap. Now its saying that I have bad egr flow again a bad o2 sensor and bad manifold pressure. I dont really seeing my egr going out this soon considering they just go bad by getting dirty and I checked it it is clean. I think that some kinda vacume issue is causing all the trouble. Any ideas.....

Leaking upper intake gasket perhaps? As for the EGR code take it off and clean it. As for the O2 sensor code your other problems are probably causing it to trip the code.

Wouldnt I be able to detect this upper intake leak by spreying either on the top of the engin? I sprayed the whole engine down with either really good several times and I get no surge...

When was your last distributor cap and rotor change?

Have you checked your fuelpressure at idle?

If your EGR code keeps coming up. Have you checked you cat convertor. My EGR code was coming up on my 95 blazer because carbon chunks kept getting stuck in the EGR and keeping it open. I had to clean it often. This was apparently caused by a bad cat converter. Mine was no good so I had it replaced and haven't had the problem since. Although now I have a leaky full injector which will also cause your blazer to idle rough at a stop, but since you don't have a running rich code its most likely the cat converter. Hope this helps.

if the egr code come sback, clean the EGR valve again.

Also check for your CPI injector leaking which is the #1 cause of the carbon in the first place.

BTW, EGR code doesn't mean replace it, clean and reinstall.

I would also say the EGR valve too. If you clean it and that works since you already replaced it I would clean out the ports.There may be enough build up there that it will keep working its way back into the EGR.