hesitation problem egr? pls help

[excoupe23]

I am having a big issue with my 91 ex coupe auto. I have been experiencing some serious hesitation in the rpm range 1500-3000 where the car feels like it is fighting to pick up speed and backfiring even though I have a new muffler high flow cat, new o2 sensor, new distributor, checked ignition timing etc.,. I was told it could be the egr valve so I drilled out my egr ports and cleaned them out well and also replaced my egr valve last year and it was cleaned b/4 installed. I think the egr is good b/c I get no codes and the diaphram holds vaccum when I place my finger on the line and press the diaphram up it stays there. I am sure there are no codes. After I cleaned the egr ports the car ran fine for a couple of days and the problem came back again. What else can it be? I have already tuned up my car--doing everything. any suggestions would give me an idea? I tried driving the car w/o the vaccum line connected to the egr valve but they sucks b/c I waste more gas, the check engine will then come on and the hesistation is still there.

[mpumas]

Backfiring???? Have you done a compression check? How about valves? How many miles on the engine?

[excoupe23]

I did not do a compression test but the motor does have alot of miles 180k, this problem also starting happening after I changed the oil last month and I never used 5w30 which is the recommend weight until now. I was always using 10w40 but I don't know if that mattered with the compression that much

[mpumas]

I would not be using oil any lighter then 10-30. The backfiring problem is interesting. Possibly leaking valves, distributor problems. I think a compression check is in order. You might pull the distributor cap and check the inside of the cap for containimatio nnmtairooigjtpu mou ou

[mpumas]

Also check for stored ECU codes. It may give a clue.