Guys
I have a 2004 Z71 double cab 5300 motor with 14,xxx miles. It has a surge with gentle acceleration when it is cold. It also always has an offensive smell. Not sulphur but maybe a hint of alchol. I am burning 10% ethanol. Mileage is disappointing at 14 to 15 on two lane highways. Chevy says all is ok by their machine and it has set no codes. Any ideas?