2003 V40 with 43k miles. Owned it since new, and very well taken care of at the dealership.
About a month ago, I switched from Super unleaded to reg. unleaded, I read somewhere that it was ok, just some loss of power.

I guess, it was worse than I thought. The
"Check Engine" light came on. It read code "P0299", Turbo charger Underboost.
The car drives very sluggish, no turbo charge at all.

Seems like the ECU reacted to the change of octane, and stopped the turbo from kicking in.
I went back to Super unleaded right away, probably used a total of 1 1/2 tanks of lower octane only.
Would resetting the ECU re-activate the turbo, and if so, how do you reset it.
I tried disconnecting the neg from the battery for about 2 hrs, then let the engine idle for about 15 min.
Ran a lot better, but definitely not where it used to be. I want the power back !!!!

Please help. Thanks.