I've recently installed two different brand exhaust systems from cat back on 93 240 and the noise is the same. It sounds like a bad Honda exhaust exhaust tip and occurs only when starting the car each time (warm or cold) and accelerating up to about 35 mph. After reaching 35-40 mph, the system is quiet. Could it be exhaust leaks or heat riser. I'm thinking about welding the joints. The exhaust system on the car now is Starla and the one I put on it before was Bosal. The old system was quiet. I probably should have used the Volvo exhaust kit or IPD's sport system.