I think you may mean the FPR may be "closed," as "completely open" (free-flowing) would minimize fuel pressure and probably give insufficient flow from the injectors. Regardless, if the flow pattern is a "stream," they probably ought to be cleaned or replaced, as it should be more of a "cone."
There's a test you can do by sucking on the FPR vacuum hose that attaches to the right (rear) end of the fuel rail. I don't recall the behavior to be expected. In any case, that hose itself may be compromised (much more likely than the FPR, actually), so it may not really be a valid test until you replace that hose. A 99-cent length of 3/16" vacuum hose from NAPA will do it, but you'll spend a good chunk of time getting behind the air box to put it on. One foot of hose did it for me, though I wouldn't have minded having another few inches to work with, so I'd spring for two feet if I were doing it again.
Also, if you have a pretty good idea you're going to keep this bike, or your friend is, go ahead and replace the two lengths of fuel return hose that attach to the FPR, along with the one-time-use Oetiker clamps that hold them on. Since there's so rarely a reason to disassemble that part of the bike, there's no reason to leave the crusty old hoses back there and have to come back in and do it again.
You can check the actual fuel pressure by inserting a pressure gauge into the fuel supply line at the front of the fuel rail using a t-fitting. You can get a cheap fuel pressure test kit at Harbor Freight. (Ignore the stuff on the box about it not working with Bosch FI systems. It works wherever you can put in a t-fitting.) You're looking for about 36-37 PSI.
Another likely culprit is the "z-shaped" crankcase vent pipe, which is a black rubber thingy visible at, again, around the same area of the rear of the engine, just up from the rear of the fuel rail. If it's cracked (almost a certainty given the age and storage conditions you describe), it will suck unmetered air into the intake, which will cause the engine to run lean and weak. This is a $16 part (11 15 1 460 480) which can be replaced without removing anything else. In fact, it would be worth starting with this before you go unbolting stuff to get at the FPR.
Also, take out the air filter and whack it on the ground a few times to get crud out. They're way oversized and don't frequently need replacement, but they do suck in dirt. Open the three spring clips on the air box, then wiggle and nudge it out the right side. You'll have to remove the diagonal air intake channel if present, which is easiest to do by removing the two bolts holding it to the radiator. It just pulls out of the oval rubber ring connecting it to the air box.
