Engine surging under low boost
I guess I jinxed myself 2 weeks ago by install a straight 4" MBRP exhaust. The truck has 10,460 miles and has performed flawlessly until a few days ago. It started to gently surge at highway speeds of 55 - 65 mph and boost levels of less than 10 psi. I checked the oil level and it was 1/2 quart low. I topped it off and ran it another week with the same problem. Today I did a complete service including oil, filter & fuel filters. I also figured it was time to clean the EGR valve. I have seen pictures of worse but it was crudded up pretty bad.
I have since driven about 20 miles and it feels as if the surging isn't as noticeable but it is still there. Could this be related to the lower backpressure of the open exhaust? I don't have any means to pull codes at this point, but the light hasn't come on either. Maybe I can get Autozone or some other parts store to scan it for me.
I like the sound of the exhaust minus the cat and the muffler and would hate to be forced to go back in order for the truck to run properly. I should have known better than to monkey with something that was working so good!