[diesel daddy]

After doing a burn out the other day I noticed some smoke coming out from under the cab of the truck I can also smell diesel fumes in the truck. I noticed it a little before I did the delete and the tunes however it has gotten much worse and I can hear what sounds like exhaust leak from under the cab. I checked the exhaust system w installed and its all tight with no leaks. It seems to be coming out near the firewall behind the engine. I dont know whats back there as I havent looked Im guessing a flex pipe of some sort. If anyone knows what Ive done please help thanks