Just saw this. I put a PCIII on my first FJR at 6,000 miles. I had bought Holeshots and by riding to Las Vegas and letting Dynojet put my FJR on their dyno to develop the 'Holeshot map' I got the PCIII for free.
I didn't think there was anything wrong with my FJR's throttle response but figured it would be a fun adventure. Well, once that PCIII was on I found out what smooth throttle response was. Holy cow! I could have lived with it in stock form, but a definite improvement with the PCIII. Downside is my fuel mileage went down about 15% from high 40s to low 40s. I kept the PCIII on my FJR the entire time I had it until it finally went bye-bye at 226k miles.
Back in late 2006 when I bought my 'spare' 04 FJR, it was advertised with a PCII. When I flew out to San Jose to get it I took it for a test ride. Throttle application in corners was NOT smooth. After the test ride I asked the seller about the PCIII and he told me, "oh, we took it off. It's in the box and goes with the bike". So I wasn't crazy. Well, I enjoyed the high 40s fuel mileage I was getting with this FJR so I never re-installed it. Throttle response doesn't bother me anymore so I guess I just got used to it. Or doesn it improve over time???? This 2nd FJR is hotter than my first, and my theory is lean fuel injection has something to do with it. So I am wondering if the PCIII would cool it down. Someday I will install that thing just to see what it does.
I don't think PCIIIs are necessary, but can be of benefit. Especially on earlier FJRs, both Gen I and Gen II. Then again, not all FJRs are created equal so it has to be evaluated on an individual basis. And as I said above, on my first FJR I didn't even know what I was missing, but boy that throttle sure was smooth after installing the PCIII.