Question on midrange burbling ??

When I first started the DL50 it was burbling a lot, and also had a lot of misfires, could not tune them out, so I did the adjustment of the metering leaver and got most of the burbling and misfires out. Depending on the weather it still burbled a little on some days. The metering adjustment was done with a 23x8 Xoar Sword.

Last week I had a bad landing and spread the gear on my Pitts and had a prop strike and cracked the Xoar 23x8 prop. So I reverted back to my break in prop a Xoar 22x8 Sword, to my surprise the engine is burbling again in the mid range, although not as bad as it stared out.

I have attempted to tune the needles on several occasions, but cannot get the burbling out with the 22x8, you can hear it burbling, gurgling and farting in this short clip of my Pitts in knife-edge at a 1/4 to 1/3 throttle with the 22x8 Xoar.

http://www.youtube.com/watch?v=QLWrG0ZPCjo

The power is great and it has never flamed out, but it would be nice to have my cake and eat too.

Does anyone have any thoughts, as to why it burbles with a 22x8 and not as much with a 23x8 ??

Thanks
Geppino