Danix, I have done a few auto-x events in my Golf TDI this year. My next time out will be with my new, fresh MAF, thank you very much.
If you are running street tires on your 17s, you should run in STS (Street Touring Street Tire). Street tires are DOT tires with a wear indicator rating of at least 140. This excludes the DOT race tires allowed in stock classes and street prepared classes. Other mods allowing in STS are: chip, exhaust after cat, air filter (cone or panel), shocks, springs, anti-roll bars, wheels up to 7.5 inches wide, and tires up to 225mm. The nice thing about STS is that you can auto-x on your everyday tires and you can be competitive without modding your car until it is unstreetable as is common in street prepared.
My car has Upsolute, Piper-X panel (when I am brave enough to put it back in), Shine Real Street suspension, 16x7 alloys, Bridgestone RE-71 in 205/55-16 and a Schrotch harness. While I am rusty after being out of auto-x for about 9 years, I think my car can be competitive, especially on shorter and tighter courses requiring power coming out of turns. I agree with Rabbit GTI that 17s are for show only and will slow you down. I went with 16s to get a shorter sidewall then on 15s and keep my overall tire height the same as stock as these wheels/tires are my daily drivers. At this point, I feel my Golf TDI is geared as low as I would want. Shorter tires (lowered gearing) would require even more shifting and may be detrimental to fast times. While this tactic does work on high revving gassers, the TDI's torque makes the car very flexible with the current gearing.
Have fun and let us know how things work out.