Sry if this is a stupid question but if you have a pretuned car with a b18bls turbo and say you blow your motor or it just has high millage or is losing comperession. If you drop the exact same motor in it would you have to retune? This hasnt happend to me but iv always wonderd this. And if not if you upgraded rods and pistons you would you?

 

Pistons and rods for sure it will change your compression specs, and for the engine yes you should because no 2 engines are exactly the same,they ware differently, you could probably get away without it but i wouldn't suggest it, this is just my $.02