You'd be surprised how much hp and torque stock parts can handle but the tune-up has to be spot on. My little 318 made 40-50 Dyno pulls at up to 22 lbs. of boost and survived no worst for wear. All pulls were done with C-14 and A/F ratios were closely monitored. But it only takes one full Throttle blast going Lean or insufficient octane and say by-bye to the ringlands and rings. Don't ask me how I know.