I have a smog pump system on the Silver Z that I recently bought. I am told the smog system was removed years ago when the car was fairly new. Now the smog system seems to be working well as installed. When I compare the exhaust smell of this car against non smog cars I have or cars with smog where the pump has been "devaned" there is a big difference. The Silver car just does not "stink" like the others. However, the car does have an exhaust "pop" when you let off the gas at medium or high RPM. Any ideas on how to solve the exhaust popping noise?