I want to upgrade my engine to produce a little more power but do not want make it loud or spend $3000 in purchasing the J-spec FS-ZE. I'm thinking of getting a FS-ZE intake cam plus a J-Spec reprogrammed CPU and complement it with a MP3 Racing Beat Muffler (to facilitate increased exhaust because I notice that the current stock exhaust is pretty restrictive). Does anyone know how much HP gain i will get from this? I'm willing to sacrifice some low rev torque for mid/high end HP. Would there be any compatibilty problems? Also because the P5 is 4 inches shorter, I assume its muffler would be shorter than a MP3's. Would modifications need to be done to the muffler? And since the P5 has a shorter muffler, does that reduce or increase overall power of the P5 compared to an ES? The 130HP/135 lb/ft torque measured at the crankshaft, so I was wondering whether there are power differences between the ES and P5.

 

This is also the route I'm going to take with my Pro5.

Get a K&N Air filter that will fit in the stock box. It provides a very subtle increase without all the noise from the open airfilter.

You can try different exhaust but most of them will most likely be louder than you like. The MP3 exhaust might be a good idea if it actually fits.

I personally would wait for a better set of cams to be produced. The cams available now will give a slight increase but honestly probably not enough compared to what a good set of cams, from aftermarket cam companies, would provide. Email those guys and ask them to make some. They won't do it if they don't know there's a market. I email each of them at least once a month. They won't respond but they will take note of it.

I don't know if the J-Spec ECU will work, hopefully an aftermarket company will eventually produce one for us.

A set of underdrive pullies will also help you out, without any noise increases.