There are a thousand cars in the game with all kinds of combinations. What works best in the PP system is a good chassis with a peaky power curve like the NSX. It already has a great chassis and the best type of power curve, which is why it's one of the top cars at it's PP level. I tried to improve upon it by swapping in all kinds of engines and nothing was faster. I tried swapping it's motor into other cars and they were still handicapped by their handling. I tried decreasing grip a little and adding more power and the car was slower. Believe me, I tried very hard to break the system and I couldn't do it in months of trying.