1984 GPZ1100 running rich

New to the forum, I recently bought a 1984 GPZ1100 and it is running rich. Runs well and idles fine but I''m choking out my riding buddies and fouled a set of plugs. I pulled the tank to try and fix the fuel gauge (Another post of mine) and the check valve seems fine, not hung up. Fuel pressure regulator?? Any suggestions appreciated.

You could run a hotter plug so you can choke out your buddies a lot longer without fouling.
You need to keep the spark plug tip between 932°F-1472°F so the spark plug can self-clean.
Temp too low-carbon fouling
Temp too high-pre-ignition

Either cut down on fuel or increase air flow.
Not sure how easy it is to check fuel pressure on the fuel rail.

Your throttle position sensor may be an issue.
Tricking your computer into thinking you are ingesting more air than you really are.

Check your air filter for restriction or if you are desperate and running away from something...toss the air filter. Just get a new engine at your next oil change.

Check exhaust pipe temps with infrared gun.
Point at a not shiny surface. See if all pipes are at the same temp.

I'm not an expert. Just guessing at a few things.

I had similar issues with my 82 GPZ1100 - plugs looked like black velvet !
I believe my real fix was replacing the fuel pressure regulator - pressure at idle should be about 33psi and up to around 36psi when running. Mine was at or above 36psi at idle - doesn't seem like much but made a HUGE difference- all plugs are nice and tan now. Also- make sure the battery ground that mounts to the right rear side of the engine is nice and clean - mine was over paint/corrosion and had a weak spark. Once cleaned up the spark went from orange/yellow to bright blue/white. Wouldn't have believed it if I didn't do it myself! Also I would check the air and engine temp. sensors to make sure the are connected and within spec. Still fine-tuning mine. 
Best of luck !

In no particular order:

Clogged / dirty air filter
Air temperature sensor / wiring
Engine temperature sensor / wiring
Fuel pressure regulator
Fuel tank check valve
Throttle position sensor (the setting or the TPS itself)
Fuel injectors 
Air / vacuum leaks
Intake boots
Weak spark (coils / spark plug wires / corroded wiring harness)
Weak battery

How many volts are at the battery, with the bike running at idle?  And over 3,500RPMs?

How old is the gas in this bike?  Is the inside of the gas tank clean, and rust-free?

Also, make sure you have the throttle body "choke lever", in the OFF position.
 

Thanks to all, I will start picking away;)