i can offer this turd of knowledge to this discussion.  we had a problem
on my moms 99 golf AEG 2.0 cross flow.  it missed and ran bad especially
in wet conditions.  my mom spent 2k at one of the local bosch authorized
shops this shop has been around for years and is highly recommended,
trying to get the car fixed.  in the end we took it to the dealer and they
figured it out in 2 hours.  the problem was the wrong plugs, the bosch
place had put "regular" bosch plugs in and that car needs bosch multiprong
plugs to run right.  the car has run well for two years now.

jonathan