1976 Blazer, 350 and Edlebrock carb. Headman headers dual mufflers and pipes bent 90 degrees behind rear wheels. Exhaust odor has been driving me crazy. I've read the other posts. I'm getting a gas smell too, what an engineer would call tramp gas from under the hood. The previous owner removed the AC compressor and lines to the evaporator. But the box and drier are still there. The heater core is working and so does the heat and blower fan. I'm on a project this weekend to stop the insanity. So, before I go too far with the "Great Stuff" Any advice would help. First, I am going to trace the exhaust pipes and look for any pin-hole leaks, and weld them. Second, I am going to spray "great stuff" in any crack or hole in the firewall, floor, and gap around transfer case shifter and rubber boot. Third, I may go so far as to seal up the air intake in front of the windshield. Is it too crazy to run an exhaust stack right up out of the engine bay? This is next. Home made, exhaust stack on one side and snorkel on the other. If I fabricate a snorkel, I'm putting the air filter on top.