But to answer your question...yes, you will loss power

 

that is a mighty fine looking sammich...

 

The capabilities of the stock computer to compensate for no exhaust is only as great as the fuel management system. Sure, that power previously used to expel the exhaust gas can be used for +HP, but as stated above, without the constant back pressure you're relying on the system to maintain the proper a/f with one less known constant.

 

You won't lose power from not having an exhaust, what kind of crazy question is this. We don't have a turbocharged engine, so I don't know why we would need any backpressure cause the exhaust gasses are all going one way. Man, if we keep getting questions like this or keep going through topics that can be very easily reserched then I might have to sell my Z and go to something else lol.