It's going to run better, without a rejet it will still run fine, but will probably be just a hair lean. You can probably compensate with the needle a tad unless you are already running that at the lowest point with it.
If you can't afford a new engine sooner than not then maybe pass on the pipe for now, it will kill any engine faster, it's the nature of deriving more power from anything. If you get one if these expect to also invest in heat wrap, these pipes sit right under your left leg and sit high enough that you'll end up very close to it. Jeans don't help you need to cover it or your leg will get toasty.