how about dump a tank of injector cleaner thru it..cheap, easy and it cant hurt.....

also (of course) replace air filter, plugs, leads, dizzy cap/arm and get valves checked (unless these have been done recently)..check cat function and make sure the car is fully warm when you take it for the test (i.e 20 mile drive at 3000 rpm or higher).

I would also do an oil change first (cant hurt can it...) and make sure all the intercooler/turbo piping is clean (dont need to be burnign oil from the pipes)- also clean throttle body/manafold and check flame trap (dont need more blow by than u have to have..)

should set u back $100 in parts and an afternoon (or day if your not familier with the proceedings) - bet it makes a difference though...

I found that when I did the above my turbo changed from being a no go - lots of go car to justr being smoooooth accelaration (all be it a lot of acceleration) and its imporved the MPG by about 10%...now i must have had unburnt (or partly burnt) fuel before which is hydrocargon....particularly on acceleration...

If you car is a no go- lots of go car...do the above, bet it helps (and it cant hurt!)