The reason im asking is becuase I dont plan on reving the engine past the stock rev limiter of a virgin PR4 ECU. So should I do or not? Do I need them, do I have to tear the engine down completely? Of course in the future I'll be tearing the enigne down to rebuild for all-motor. But the engine is just going in stock for now, just so my car runs. they only cost $50 (or less) should I spend the extra money and do it now, or do it later when I rebuild for all-motor. Engine is completely stock, other than the Custom IM. But it will not see rev's more than 6500 or 7000.