Received my Active Exhaust pre-muffler last week. Working on install. Very much looking forward to getting it dialed.
Two mods that I am VERY fond of for 3.2s are the KW V3s and Sal Carceller MAF / injectors / DME ECU. They represent quantum leaps in technology and decades of development past what was available in '84 - '89. M&K's development of a valved exhaust may well be the third candidate for that list.
Added bonus is that the M&K Active Exhaust pre-muffler is lighter than Dansk pre-muffler, stock cat and gutted stock cat...
http://forums.pelicanparts.com/porsche-911-technical-forum/1070460-m-k-active-exhaust-install-87-3-4-stock-cat-s-dansk-bisi-etc-weights.html
Kudos to Brian for continuing to innovate in this space.