If you pop the seat unit and have a look at the ECU underneath the storage space, you may notice a silver sticker on the top of it. If this is missing or broken, then it has probably been changed.
Course if professionally done the sticker will have been replaced as it is waterproof.
Best way is to peel back the sticker, pop the rubber bung underneath and have a look at the chip.
I've got 45mm Arrow cans on mine. When I got it dyno'd at Hobbsport they couldn't believe how poorly the Arrow chip performed on my 916. Apparently 45mm are designed for the 748's. Advised me to put the original chip back in or get an FIM chip. Got a FIM chip.
For the sake of £40 or so its worth doing the whole job and getting it set up right. I've got cored standard cans on my bike and the JHP chip and Nellys set up has made a huge difference. I ran it on the standard chip for nine months and i thought it was okay but nothing special. Nelly set it up still on the standard chip and it was transformed. Went from 50mpg to 62 mpg. The JHP chip and set up has made it smoother everywhere, especially at low revs.
Interestingly my standard cans are made by Arrow.
The sticker on the ECU could also have been removed to twiddle the trimmer pot in there so that isnt always a good guide. The only way is to tell is to take the bung out and look at the number on the chip then give JHP a bell.