how can you tell if somebody has sabotaged your gas tank?

[JohnnyRingo]

9. It's almost never a fuel problem.

Alway... check ignition first, second, and third. More people have compounded their problems by attacking the fuel system first than you'd believe.

I know it sounds like it isn't getting gas, and it acts like it isn't, but the fact that it drives above idle says it's an ignition problem. It could be anything from the oxygen sensor (likely), to the ignition module (possibly, but not likely).

In French, the word for "leave it alone" is carbureteur. The Wright Brothers flew with a soup can as a carburettor. They either work, or they don't work. It may run rich or lean, but it'll run. Injectors are even more reliable.

If you really think you have a fuel problem, unhook a fuel line near the injector block, and with a glass jar under the open line crank the engine for a few seconds to fill the jar. Leave the sealed jar to sit for a couple hours and see what it looks like. Any foreign substance will settle in a strata layer, water at the bottom, and lighter solvents at the top. Ths is how pilots check their fuel for contamination except of course, they drain it from a tap in the wing.