Lexx. I looked into the GTM kit when I bought my HKS kit from them. There have been a few issues in the states with kits they have sold having a lot of missing pieces. GTM are also quite possibly the most ignorant company I have ever dealt with - They are brilliant, right up until the point they recieve your money. After that you will get more communications from a brick wall tbh.
You also don't need a TD exhaust but it does help & a turbo timer isn't necessary either but it isn't a huge cost at the same time I've done a lot of research into the GTM TT kit so if you need any advice drop me a PM