It's funny how a post like this comes up right after I fix a similar problem on my Z.
DAVE...
Not sure if you are experiencing the same issue I had, but over time I noticed a strong smell of gas/fumes. First, try this. Take a short drive making a few "spirited" accelerations. During this, make sure your windows are up and your AC & interior ventilation is off. Just before you return home, cut the AC on. Does the smell get stronger?
This was the case with mine and I was able to quickly determine the smell was coming from the engine bay, not the exhaust (because of where the AC inlet vents are located).
What I found was that I had developed a very small fuel leak somewhere on the passenger side near the rear of the plenum. In my case, I had a small amount of moisture and dust gathering on the valve cover just behind the #6 coil pack. Despite the evidence of a leak, I could not determine where the leak was coming from.
Ultimately, I took my plenum completely off and removed the hard fuel line that leads to the fuel rails. I replaced the O-rings in the fuel line, used stronger clamps on the rubber hoses attaching to the hard fuel lines, and replaced my lower and upper plenum gaskets. The lower and upper plenum are to be attached using a specific torque sequence tightening bolts to around 13 N*m. I was surprised how light this setting felt. So it is very possible you have overtightening on the plenum.
This process solved my problem, though I cannot say which specific fix took care of the culprit. All total, I think I spent about $15 in parts and a day in the garage taking my time to address the issue.
If the AC trick doesn't make the smell in your car increase, then most likely it is your mods causing your car to run a little richer and is perfectly normal.
