You may want to try one thing before using solvant as a last resort -

I removed the stiff side liners, floor carpet and the bulkhead carpet (peel it off the adhesive - a lot easier to clean) then took them to the car wash and blasted them after soaking in some strong detergent. The stiff side liners are tricky since they have a molded solid backing. I worked the spray to push the rinse along the surface, going from center to the edges. It is possible to get most of the stuff pushed off.
As for the carpets, since they can be blasted through the fabric, it's easier to clean more thoroughly.
Afterwards, the liners were aired out for several weeks, sometimes in the sun.
The odor is gone but it took plenty of quarters for about 5-6 rinse cycles.
I was lucky the fumes didn't get into the rear seat cusions....
Don't forget to thoroughly clean the metal surfaces and soak up any fuel that accumulated in nooks and crannies..