Trying to sort out a preowned '06 and found it had a needle with 3 grooves.  Which position would be the same as shaving 1/2 the white spacer using the stock needle or can the 3 groove needle even be used?  I think the previous owner tried using the dynojet kit and I wound up with a bag of mismatched parts.  He changed the air screw mixture screw also and I can't get much response when trying to adjust so may have to change it back to stock.  I have a 52.5 pilot jet, 152.5 main jet running a short ryca header pipe with a stock dyna muffler and cone filter.  Bike runs ok, but backfires (pop pop pop) on decel, surges a little at low speeds, and takes choking when cold (75 degrees).

Just the usual poping

there are at least 2 styles of idle mixture screws and it's not obvious which one goes where.

so if you have one that 'looks original' I'd go with that unless it's a dead ringer for the new one.

then if you can screw it all the way in and it does nothing, the pilot jet is too big.

I'd only be concerned with the tip, not the head.

I just found a small bag of misc. carb parts that the previous owner had left in a tool bag.  Looks like pilot, main jets, original needle and 2 needle jets that are marked X7.  Some parts don't even look like they came from a Mikuni carb.

Suzuki’s needle jets and jet needles for this carb are:
NJ:  X-6 & X-7
JN:   5C17  & 5C39

5C39 has only 1 groove for the clip.