F4i sounds like v-twin
 

I know the first comments are going to be to use the search button. But I already did and my issue seems a little weird.

I was working on my F4i yesterday and had the fairings off. I started the bike and revved it a little with the right side fairing off and everything sounded/worked fine. I put the right fairing on along with the seat (no other changes) and then started it up and it sounded like a v-twin and has no power. What could cause this? It ran perfect and without making any changes it ran like crap. This was probably within a half hour of starting it the first time and shutting it off.

I guess the common cause of this is the fuel pressure regulator. But I'm not sure that could be the issue in my case?

check throttle position sensor, as well as all vacuum connections. take another look at everything you touched. it could be from a bad FPR if it has a strong gas smell.

Taking your fairing off has nothing to do with your running problem. Start going through all the normal checks one does when something doesn't run correctly.

Kinda sounds like an exhaust leak somewhere.

The fairing obviously does not have anything to do with the problem, but i was just saying that nothing was touched other than the fairing in the half hour span when the bike was started and ran fine and when it started with the issue.

Definitely not an exhaust leak. I am pretty sure all vacuum lines are connected as i can't find any stray hoses.

There is a strong gas smell but could be due to cranking it over and over trying to get it to start. (won't even start now)

How can i check the TPS and FPR?

ok, so with the vacuum line disconnected from the FPR it does not leak fuel. From what I've found that is the sign of the diaphragm inside being bad. I may be wrong on that though

If you ruled out the exhaust leak. The only other thing I can think of is a cylinder miss fire or an injector both will give you a v twin sound and power loss.