I have been losing power, particularly from cold, but now when the engine is warm.

After exiting a roundabout or after slowing for a corner, I get a loss of power and the engine misfires. It has stalled twice.

Two independent garages have been unable to find the problem. I'm reluctant to go to a main dealer having been conned by one. Subaru have a reputation for reliability-and it is a great car to drive-but I wonder whether this could be the sign of a major problem.

I would appreciate any advice please