im not thread crapping but is it worth upgrading to GTX for the cost of almost £700 to get an earlier spool of 500rpm? it's my plan to get -5s but of course GTX is the way forward for me, however for the extra cost? thanksReal world difference is unknown yet but on the dyno a guy from Iceland is said to have been impressed with the performance spooling up some 500 rpm earlier and making a bit more power on the top end. Owen developments offer a kit for 1300 plus vat on top of the cost of new turbos and claim anything from 500-1000rpm earlier which I find very optimistic and take the info with a pinch of salt. Not many of these around but hopefully once my car is built I will have some real data for you.