[RPM427]

During a lean condition, higher boost levels will destroy the internals of your engine. The damage occurs when not enough fuel is being delivered therefore causing the motor to run lean which in turn causes detonation and extremely high combustion chamber temperatures. The detonation alone can cause pistons to crack and apply undo stress to the rods and crank and so on. The high combustion temperatures can actually melt pistons. Usually the top of the pistons as well as the ring lands will melt away causing extreme blow by and excessive crankcase pressures which can blow seals out of the motor and the end result will be lose of oil and oil pressure. Normally detonation and extreme combustion temperatures occur together during a lean condition, so you can imagine the damage that can occur.