^ You probably do not need colder plugs. But with a turbo back exhaust you should be seeing about 18 psi now under load, so you might benefit from them. I upgraded to the step colder NGK's when I went with the 3 inch catless dp/rp, not so much because I needed them at that point, but because they do provide a little protection against detonation, which would result in the engine pulling timing otherwise. At your level (and even at mine being fully catless and having the HT tune), the car will probably run well on the stock heat range.
But I did not foul plugs by going colder at your mod level, so maybe you will not. That is the issue if you do a lot of low speed stop and go driving. I drive the *&^% out of my car, so they stay clean.
