Vacuum assist and there is plenty of stud length, I have 2-3 threads poking out after bolt. Maybe you could update a 4k model to a TYP89 and then you'll have enough threads, if this for your 4k. Alexander van Gerbig -- '88 80 The Audi 80 Pages----------------- http://surf.to/the80pages.com North Ferrisburg, VT 05473