Use Amsoil in a Ski-doo?

Hi all, great forum.
I bought a 98 Skidoo SummitX 670 with 2200 miles on it. someone has swapped out one of the carbs and it hadn't ran in a few years. I took the carbs apart and cleaned then and got it running, I had to adjust the throttles so they would both rise at the same time and for a couple days it was running good. Then the night before I am going to take it out for the weekend, I bought amsoil 2 stroke, filled up the oil resivore (it had skidoo oil) and took it out for a ride and at first it ran good, but then it started running rough and the idle dropped down about 500 rpm....does this sound like an oil problem or is something else going on?

thanks for reading.

Thanks, I'll look at the carbs again. Someone else said to change out the fuel pump, that it could be causing the problem......so I might try that too.