hi Nigel,well,interesting that you ask if any diff,the bis and aircooled i have looked the same,but could be different ratings,i used bis ones(better nick),and with the spring on the bench, i measured 15cm and cut them,it works out around 1 1/2 coils,i then ground down the cut end for a seating area.
it does seem stiffer,but that could be ''sticker '' tuning.....you know,all in the head.....................but it deff goes thro the turns better,no hint of tuck in now,with the lower front end(reverse eye/cut blocks and the neg camber top links) i had it started to turn in quick and catch the back end out....thats now gone,all in all a good mod,and my turbo 1 sport -30mm coils will now be for sale.....good for some one who just wants a mild lowering :wink: