Just jetted yesterday, went with 125 main, 40 pilot, air screw 2.5 turns, drilled slide, installed adjustable needle clip 2 from top(don't have the number with me, but these were all the Kawasaki parts listed on this forum), air box mods, new air filter. Also put a 1/2 hole in the silencer baffle. It runs out a little better, not an impressive difference though. Haven't checked the mileage with mods yet, keeping my fingers crossed.
Funny thing is, I never jetted my first bike. It got 58 when new, and then I modified a KLX300 silencer to work with the stock header, and it still got 58. It was definitely lean, but ran ok.
I'm hoping for a big torque gain with the 351 so it'll pull 6th easier.
FWIW, this one seems to get 50 even when I baby it. I'm not too concerned, but I'm hoping it stays at 50 or even gets better with the 351.