I own an Audi Allroad 2004 ... just changed the spark plugs and added a seal that was missing. I had a wierd problem a month ago

drove for 15 min... went to bank stoped car... started fine... went across the street stoped car. came back 15 min later... No start

It turns, but no fire. after the 3rd try it started to smell like gas.

i goofed around with the ignition (turn on key real fast and really not long) eventualy it started back... but the idle was out of wack ... just pressed on gas and idle came back normal. very wierd.
now its been doing it alot more since i changed my spark plugs and i added my seal that ws missing in my intake(losing alot of horse power beacuse of a stupid seal. fixed it)

Might it be the timing belt.... i know i have to change it very soon. im at 103km
or i was also told it might be the gas filter or Sensor... Im only gettting 1 fault sensor and it says Engine temp too low.
i do have Vag com.
was wondering also how can i know if all the temps are he right tempatures and prssure that i read on vag come... doesn vag com correct deffects.. i dont think it does if im worng it be cool to be guided on how to do some maintenence on my audi allroad 2.7 bi turbo soo it doesnt cost mega $$ to fix stupid ****.

thanks to who ever reads my forum.