If you've been running the bike with the cans on for a while then they should be able to get a rough indication of how lean or rich the bike is running by the colour of the sooty deposits at the end of the tail pipe ( and I'm not talking about glove pupets there ).
The end can usually makes the bike run slightly more lean. As a rough guide this is what you should expect -
Jet Black - rich
light gray - lean
Sooty end means rich , which is safe , white means lean which means holes in pistons
A nice toasty dark brown is nice , but sooty is ok unless you notice the bike bogging down , also you will only get the toasty colour if you have just been thrashing it (redline , lots) so sooty on normal running probably means brown when thrashed
As a rule of thumb if the tuned length and positioning of the pipe has not been altered then usually no jetting is required. However, all bikes run better once they've been tailored to their pipe.
If you want the bike set up properly you really need to get it on a rolling road which will cost ya. Try East Coast suberbikes in Fife or Swona in Edinburger.
You can read about one mans experience here -
http://www.roadracers.co.uk/vtr.htm . After a lot of buggering about he reverted back to almost standard settings.
Description of dynojet can be found here -
http://www.roadracers.co.uk/dynojet.htm
im sure you must have seen a few of them at tesco on a sunday with their shopping trolleys