I put a new carb on my GTO several weeks ago. It's the correct carb. The prior one was incorrect and starved the engine at high RPM.
Now, with this new carb, the exhaust rumbles alot more than before when I decelerate (manual trans). I've got turbo-flows and it never did this as much with the old carb. Somethings definitely different in the exhaust sound.
Also, perhaps unrelated, the engine has been running a bit hot and knocking a bit more. It even dieseled in turn-off for the first time ever.
Timing is set correctly, 8-10 BTC.
Any ideas? This is very strange.