[V8] VAG-COM question

[NicolCS at aol.com]

As long as we are on the subject...  (and please excuse me if this has been 
asked and answered a thousand times) but what's the best way to get data out of 
the ECM on a '90?  I've read conflicting information and I've seen equipment 
where the specifications indicate '91 and up only. The Ross-Tech stuff looks 
pretty intriguing but I'm puzzed on just what to order from their offerings.

Here's what I already have:  Snap-on MT2500 with Audi-VW Cartridge to 
1991-2001 and an old Toshiba laptop that might also be a candidate for VAG-COM 
conversion.  I've never tried to connect the MT2500 (no need, car runs fine).  Is 
there any hope that it would work on a '90?  Was there a major change in the ECM 
or programming for '91?   Or, should I just skip the Snap-on scan tool and go 
for a product from Ross tech?  Does anyone have experience with the Snap-on 
gear?
Thanks in advance, 
Craig Nicol
'90 V8Q, 96k Cayenne