Not a scientific analysis, but a general observation - if you want a deep tuba sound, you need a tuba. The long slash cut pipes will always have a throatier sound than the short ones.
As for popping, you gotta match the inflow with the outgo. Open up the exhaust and you hafta open up the intake as well, and match the fuel delivery too. Read the 1000's of related threads on here and when you get it to a deep gurgle with only an occasional pop on decel, you are there..
Excessive popping usually means it's running too lean.
