Another tip to those on the list that I learned in my recent 2.1
conversion (reminded to me by reply to Jeff/Oxroad@aol.com's Vacuum Leak
Problem with his Throttle Body)

When using a replacement (new) case for 1.9's or when upgrading to 2.1
using the Digijet, VW and Bentley says to use the 2.1 Center Air Plenum
(025-133-055B).

I have mentioned before that I had to use the 2.1 Air Intake Runners as
well because short 1.9 connecting hoses are too small  to fit the hose
flanges on the Plenum.  VW/Bentley makes no mention of this.

The other thing I failed to note was that a slight modification was
needed to attach the 1.9 Throttle Body to the 2.1 Plenum.  The Throttle
Body mating flange on the 2.1 Plenum's "curl" is a little larger that
it's 1.9 predecessor.  Hmmmmm.......Looked at a 2.1 Throttle
Body.....can't use that because the intake throat of that appears too
large for the 1.9 Air Intake Elbow coming from the Air Box.

Thanks to my best bud Cliff (who's done this before), he told me to
initally install the 1.9 Throttle Body to the 2.1 Plenum WITHOUT the
gasket and tighten it all the way.  What happens is that the 1.9 TB's
smaller taper will cause the Plenum's flange to "curl" even smaller to
accept the Throttle Body's taper.  After, that remove the Throttle Body
then reinstall with the Seal.  Fit perfectly.  Does not harm, score or
otherwise damage the Throttle Body or it's taper that I could see.

Again - VW/Bentley makes no mention of this. YMMV

Oh yes - use the original type 1.9 Throttle Body Seal (new of course). 
It's also the same seal used the the Air Cooled FI 75-83.  I've got 'em
in stock (one of many "weird" things I have).

Guess ya learn by doing ;-)

Jim
84 Westy 2.1 * 62 Beetle (Father was orig. owner)
Sherwood Automotive * The Old Volks Home (oldvolkshome1@juno.com)
(916)221-5342