Hi Ive just installed a Hdi GT2 into my 06 BA mk2 xr6T, took me about a day and a half,[got a wife and kids and a fulltime job...so yea a few extra brews just to medicate me through that !] I noticed a huge improvement, maybe btween 15-25kw?, I also have a 3inch full coby system with the cats removed and just a hot dog in its place, plus I installed a k & N pod filter... car goes awsum now and I still have to get it tuned [ I havnt pushed it hard enough to spool up the turbo yet, but even so I can feel that it wants to get up and go]. Anyway if your on a budget the HDi is a good bang for your buck and the quality is very good as well, I just had to purchase an extra reducer, but I would encourage you to really study the instructions first. good luck and send me a message if you want info as I can still remember how I did mine....well sort of, bearing in mind it was a month ago and ive been self medicating while watching bathhurst over the weekend.