Fuel smell, exhaust smell, chemical smell resolved

Quite a few threads on these issues, which I believe are one.

I thought my car smelled like gas. Buddy #1 thought it smelled like gas. Newport European mechanic #1 didn't smell a thing. Newport European mechanic #2 thought it smelled like exhaust "right in your face". Buddy #2 thought it smelled like "concentrated new car smell". Buddy #3 smelled nothing. Ok, so I'm Felix Ungar. It still gives me a headache after 20 minutes of driving. Mine is a like new 2007 with 1500 miles, bought this January.

Always when moving, with top off. Nothing under hood, under chassis, around gas cap, or coming from tailpipe. Only in cabin, and dissipating seconds after stopping. If the car is not moving it only smells like leather.

I searched the forums and found #1 cause of fuel smell is a leaky charcoal canister valve - Newport European found leak with smoke test and replaced mine, but it made no difference.

Other than that the other complaints have in common is smell comes in with the top off. Some theorized air blowing overhead causes low pressure in cabin, drawing in smell from...somewhere.

A sampling of similar issues:
http://www.lotustalk.com/forums/f101/10-fix-raw-gas-smell-24596/

http://www.lotustalk.com/forums/f25/why-does-my-car-insist-smelling-like-burning-oil-72058/

http://www.lotustalk.com/forums/f3/carbon-monoxide-48045/

In the course of performing the Cobra antenna mod, I found the smell emanating from the dashboard and traced it to the fiberglass sills. The sills are hollow from back to front and open into the dashboard. The backs of the sills open into the fuel tank compartment. If there is any spillage, the passenger side will vacuum it up into the cabin.
I plugged the backs of the sills with spray foam, but it only reduced the fuel smell a bit (my other thread Dashboard Smells Like Gasoline). It was at that point that Buddy #2 switched his evaluation from "gas" to "concentrated new car smell".

I cut the tips off the stock exhaust (they're ugly anyway) and installed longer tips at an angle pointing at the ground. 3" between diffuser and tips should reduce exhaust backdraft. Drove car - no difference.

I removed the interior from the seats rearward and sealed every hole and crevice from the floorpan to the rollbar (quite a few) with silicone, and the big shifter cable hole with spray foam. Drove car - no difference.

Avoided the car for a month. Thinking about getting rid of it.

I put the shop-vac hose in the window, closed up the car, and the smell appeared immediately, so the low interior pressure theory was validated.

Ordered air bag cover clips, removed dashboard and sill covers - the smell from the sills was noxious. Big pice of gray open cell foam in the sills serving no apparent purpose was removed - they must be for sound as they weren't even touching the sides, not even an attempt to seal (not that open cell foam can seal anything). Found small leaves and other debris in the sills.

The sills are not sealed along the bottom. Looking into the cavity, I can see light off the garage floor. This is why sealing the back only failed. Outside air can draft into the sills from under the car, and pull their chemical funk into the cabin via the dash. I don't know what in them reeks. It's not the orange glue, or black glue. Maybe the insulation on the hoses? I don't care anymore, I just want to isolate them from the cabin.