RE: Jett 56 help with Jackal 50
Quite the opposite - I do not have a .56, "just" a .50 - but the Jett tanks work very, very well and improve consistency, not hurt it. I also have run them on piped .65 DF engines which pull 4oz/minute, without trouble.
If it runs on the test stand with that tank but not in the aircraft - something has changed. There has to be something else going on IMHO. The folks from Jett preach solid mounting, these engines generate a lot of power for the package size and need to be mounted solidly. I agree with rc's comments.
The big question is - when you changed tanks did the needling improve? Y - then it was something to do with the tank installation. N - then it is a separate issue.
Hope you get it worked out. Bob should be along here any time, he's "the man".
Same prop? Looks like 6" pitch but can't tell the diam.