My take on this is if you smell exhaust in the cabin you have a leak. Spoilers, tailpipes, bumper/no bumper all play a part in how bad but the bottom line is you have a leak. Find it and fix it. I'm pretty sure I still have one small leak but I need to pull the gas tank to fix it. When I first did the smoke test I had previously gone over everything with a fine toothed comb. I was so sure I had everything covered. I wish I had a video of how much smoke and how fast it filled the cabin. It really doesn't take much of a crack to be a problem. And a little thread levity never hurt anyone! Derek