Gotta say Mitsu 6 bolt 4G63. People have made over 600 WHP on stock motors. No one has really found the limit as I only know of one person hurting a motor from sheer power. Even the 7 bolt is impressive. People have made over 500 WHP on the "Weak" 7 bolt motor. I personally have run 12 flat in a 3200 lb car on a completely stock longblock with the boost set @ 28 psi without ever even changing the headgasket. AMS has seen ~550 WHP on their Evo8 with a stock block also. The stroker kits available allow you to go to 2.4 liters. People have made over 500 WHP on PUMP gas. People have run 10s on Pump gas with this motor. Mike and I have run 11's stock turbo/engine.

too much good stuff.