The 100mm CV joints are lots stronger than the original 90mm. Replace your leaking weaksauce bits with this proper stuff.
With that said, listen UP, 1.8l 8v and 2.slow owners! Whether you've got a Mk1, 2, or 3 with 020 tranny, one of the most cost-effective upgrades you can ever do is swap to a close ratio transmission from a GTI/GLI/Scirocco 16v model. (USRT recommends 9A code for easiest fit to Mk2/3.) The most aggressive is the 4K (Mk1 GTI, Mk1 GLI, Mk2 Scirocco 8v). These flanges make it a direct bolt in for any Mk2/3 4-cylinder car. Parts priced each.
P.S. ASK ABOUT AVAILABILITY! WE NOW HAVE (INCONSISTENT) SUPPLY. YOU MAY GET LUCKY.