I have a group 5 kit so I can't say what has changed from group 5 to 6, but the main things I can think of that changed from 4 to 5 are the new, adjustable engine mounts, the addition of retaining screws/washers to the gearbox output shaft seal and a shorter exhaust pipe part way through group 5.
I think they also changed the glue used to attach the magnets in the engine pulley starting with group 6 or near the end of group 5 and made a change to the oil pump cover on the bottom of the main rotor transmission which adds cooling fins and recesses the four bolt heads for more clearance with the lower fuel tanks. There may be other things I'm forgetting or am not aware of.
-Adjustable engine mounts
-Addition of retaining screws/washers to the gearbox output shaft seal
-Shorter exhaust pipe part
-Change to the oil pump cover on the bottom of the main rotor transmission which adds cooling fins and recesses the four bolt heads for more clearance with the lower fuel tanks.
Simply by replacing those parts or these changes affect bigger assemblys too
Duvan- The MFS is NO on group 6. I was in group 5 and insisted mine get changed to NO. YLF covered the other differences. I had a few magnets come loose, then rebonded with J B Weld. The new engine mounts came out in my group 5. However, they use the original studs coming off the engine for mounting. Group 4 and previous had those studs cut off . Stan
Duvan- There really wasn't a problem, but an adjustment nuisance. Whenever it comes time to tighten the belts, tightening the belts with the older style would run the pulleys out of alignment, which you would have to adjust. The new mount keeps the pulleys parallel as you tighten them. Its a very clean looking mount and it only took me an hour and a half to install and do the initial alignment in my helicopter. These new engine mounts were a big part on my waiting for my turbiine. I was delighted with the very clean and robust design they came up with. I still have not had to tighten my belts yet though. Stan
Group 4 (and 5) include various capacitors and diodes to solder to the terminal strip on the governor box to filter the RFI. However, there is now a filtered terminal strip available that doesn't need the extra components added and makes for a simpler, cleaner install. You can get it from Eagle R&D. Mike
Duvan- Just what Mike said. I hhave the diiodes capacitors and shieled governor box, and have flown a lot around high tension lines that hum in my headset, and have tried many radio frequencies . So far no sign of interference. Stan