Popping on decel usually means you're a little lean in the pilot circuit.
Yes, it sounds like your main jets are still a little too big, going back to stock 125/115 will probably cure that.
You should be very systematic about what you do and only change one thing at a time. Do the main jets first. Start with tuning the highest rpms at WOT first, then do the mid range, then do the lower range, then do idle.
You also need to make sure the carbs are synched very well. I had to do this more than once to really get things right.
The bad news is that you might be removing the carbs several more times. The good news is that you'll get very fast at it. This is the price you pay for using aftermarket parts.
Remember, start at the top and only change one thing at a time.
I would leave the pilots alone and just fix those mains first. Test ride the bike and observe. Once the higher range is sorted I would hit the idle systematically. Adjust both idle mix screws by a full turn in an arbitrary direction (just remember, or better yet write it down) and test ride it and observe. Now, turn the idle mixture screws a full turn again in the same direction and test ride the bike again. Keep doing this until you see a clear difference. Do this and you will know for certain whether turning them out increases fuel or decreases it. I don't know anything about the maxim carbs, so I don't know if you have a fuel or an air mixture screw.