Jet kit or shims? any thoughts

[neillebbernB600Y]

Hey folks
I have a B600Y (2000) and am considering a jet kit. I had a mate post a question on my behalf (Bandit 600, Throttle Lag up to 6K) and thanks to those who replied, the verdict’s ‘its too lean’.
Have adjusted the a/f mix slightly (and UK models don’t need any drilling) and will be shimming the needles as soon as I can get hold of them. After looking at other questions and answers am I right in assuming the standard air filter is the best way forward (even if re-jetting), what about the snorkel, should it be left in place if the needles are shimmed and are new, bigger, jets any huge advantage?
Will a jet kit give me any real difference in performance over shimming and how much will it affect mpg?
If a jet kit is the way forward can anybody recommend a good kit available in the uk for the B600 that they have had good results with, or maybe highlight any to avoid. Also how much is the timing advancer necessary and do they come with jet kits.
One more thing, if the carbs are re jetted do i need to do a dyno test or will it all work well out the box (guessing thats too much to ask)
Sorry there are so many questions    but I’m keen to learn if nothing else.
Cheers guys  neil

[Ranger]

[neillebbernB600Y]

thanks for the tips
have added some shims which seems to have helped but i think ill try one more on each (will bring the total to 1mm or 0.040") will put the proper jet kit on hold for a bit i think as am a bit short on cash.
Just a quick one for you Ranger, when you shimmed the stock nedels did you replace the jets or keep the standards. Mine are only 92's i think which seems a bit small.
  neil