Well my car (who was owned by Mik before me) cracked his stock block at 370 KW at the rears with a Tomei stroker. However this was a Series 3 R33 and from what i can gather these blocks were quite porous
Tomei Expreme Manifolds
2 X GT RS's
Mines dumps
HKS 70 mm into 80 mm front pipes
and a Trust MX 3.25 inch cat back i think it is
Big enough for roughly 400 KW at the rears (give or take a few KW)