Been around Z's a while and know most usual suspects in gas fume and exhaust issues with these cars, but......
Series 1 car, I have dropped tank, replaced all vent lines with no kinks, pressure checked expansion tank on right side, checked for fuel leaks front to back.
The issue is raw gas fumes present in garage when car sits overnight, and sometimes driving with certain combinations of window configurations (drivers window down and passenger window cracked).
Checked filler tube seal, filler tube vent line to expansion tank, replace PCV valve, all lines to flow valve guide are good.
No exhaust fumes at all, just raw gas.
The car has after market Webers with the little rectangle air cleaners, this is the only thing I can think of that may be the issue because the stock air cleaner isn't on the car.
Any thoughts?