Yes, the engine limp mode can cause the rough idle and lack of oomph.
First thing to check is the DESS key. Make sure it is on good and tight when you start the machine. Even hold it in place while starting.
The next thing to ask your friend is did he give you the right DESS key? (i.e., does he own multiple DESS machines and got it screwed up)
From there, getting a code reader and finding out what the computer is thinking is wrong would be next.
2015 Skidoo Renegade BC 600 Etec
1996 Skidoo Touring E 380F (sister's)
1995 Skidoo Summit 583 LQ
1985 Skidoo Tundra 250F
1999 Arctic Cat Jag 340F
1999 Arctic Cat Z 370F (son's) - needs track
Currently working on:
Kiddy Caboose - older Nila sled.