Did you get a MIL eliminator with the Helix downpipe ? If not then you need one. The Helix pipe is completely catless and will set a p0420 catylyst efficiency code. Pony express performance has them. The cruise automatically is disabled when a code is logged.
Same thing happened here: mine is just over a 1k and totally stock. I was driving on the freeway with very low gas in the tank, the car hesitated and the CEL came on as well as the flashing cruise light. I thought I was running out of gas and I took an exit right away, filled up but both lights remained flashing.
I then contacted my Subie Dealer and he advised to disconnect the battery, I also pumped the brakes, waited a few minutes, reconnected the battery and all symptoms disappeared.
I am a bit worried guys and would like to know what happened and if this is gonna happen again in the future. :roll: