Here's what I did to my carb. I'd never messed with one before but after joining the forum I felt like there were symptoms I had that could be corrected by working on the stock setup. Mind you, I had put an after market exhaust on but as I worked through the issues I found that taking things slow and doing one thing at a time to see the results worked out well for me.

1st mod was to change the needle jet spacer to a #4 nylon spacer from ACE. Eliminated the surging in the mid range I was getting from day one.
Changed to a 150 main jet after a month or so to improve the high end some...that worked!
Still had the POP on shutdown and pops between shifts (pretty sure I don't have air leaks in the exhaust)
Threw in a 52.5 pilot jet with bleed holes and that (almost) eliminated the shutdown POP but still occasionally get pops between shifts.
Fine tuned the airmix screw to 2 1/4 turns out.