Hello guys, I have been having an issue with my 91 Olds 88 Royale for a couple weeks now. Its a somewhat load roaring kind of noise I am getting whenever I start to accelerate from a stop light etc... Its goes away after I hit 30 mph. I am thinking the muffler or catallitic converter is the cause because I had someone push on the gas pedal as I looked under the hood and around the car. I discovered that its definitely related to the exhaust system since I could hear it make a popping sound when it revved up. I recently had a tune up done including new plugs, wires, fuel filter, transmission fluid change along with having the O2 sensor and trottle position sensor, as well as a new starter. I did the paper clip test for any codes and it did show a 27 and 28, however no check engine light. It has 195000 miles on it now. I did have the muffler replaced about 5 or 6 years ago and it does have some rust along one of the edges and a tiny rusted out crack on the bottom about the size of a finger nail. So what are your thoughts on this????