1red5 wrote:...to this:

I have one of this fitted to my SP.
The purpose of fitting this device was not to increase the boost, but rather to ensure I get the factory set 8 pound boost. Mazda replaced the turbo under warranty. But I later found out Mazda fitted a smaller wastegate which reduced the boost to a paltry 5 pounds.
So when I got my engine rebuilt with better internals, David @ MX5 Mania also fitted the Turbosmart Boost Tee, to bring back my boost to the factory specified 8 pounds (apparently I can increase it further, but I just want my SP standard).
It was set and fitted two years ago and I've never had to touch it again since. So in short, it's been very reliable and performs as intended.