Got stock internals on D-series, got everything ready now to turbo, but still a little worried about compression. The pistons have been ceramic coated, but otherwise they are stock (0.20 thou over sized). The manual on my car says compression is 9.1:1 stock, but the block was decked and the head skimmed. Should I just boost the car at a low boost like 0.4bar on the stock internals or should I buy one of those HKS 1/2/3mm headgaskets? Which will be safer?