I have a 2011 outlander 800 can I run a slip on exhaust without an optimizer? Is it safe to run it without one? I've heard it will cause it to run lean and cause catastrophic engine failure. Thanks.
You should run a tuner. Those "optimizers" are crap. Run a PowerCommander 3 or 5 with a proper tune. These guys in Edmonton have a chassis dyno and the know-how to make it perfect:
The EFI will not adjust for the pipe or any changes to the intake (snorkles, free-flow filter, high-flow intake). The 06 to 08's were OK with a slip-on pipe as they ran a bit fatter. The 09 and newer will run VERY lean in the low and mid range, slightly lean in the high end, and will be noticably hotter when you add a slip-on pipe. Lot's of guys do it...but it's not a good idea.