what can i do to my infinity to make it faster

Headers, turbo or supercharger, NOX injection. The last three will eventually detonate the engine unless you do some serious engine work. Computer mapping, I suggest you find a speed shop, they can get headed in the right direction. Remember speed can get expensive.

I can't imagine why you'd want to make this car faster. But I'd start by assuring that everything is working and in tune to begin with. After that, I wouldn't touch it, but you could chip the computer. Anything else will be overkill in a car that's not likely worth over five grand.

If you seemed to have lost power the head gasket may be going bad . A new motor properly broken in will give you a boost .