it could be anything from a blown plug to a gasket problem,you need to have the ecm checked for fault codes to point you in the right direction
I'm having the exact same problem with my 96 Explorer.
Your Subaru is misfiring when it reaches 1 bar because it has a mechanical problem.
I am having the same problem with my Ford Explorer 2011. When I accelerate to 60-65 I start smelling the smell. I have had my car in and out of service for the past year about this smell and they finally told me it is the carburator.
I had a similar problem and it turned out to be a loose hose connection to the PVC valve.
2008 malibu 3.6 L code says PO302 misfiring Misfiring in number 2 cylinder. Could be an ignition problem with a bad spark plug or spark plug wire. Could also be a bad fuel injector. Could also be a mechanical problem such as a bad valve. Start with new plugs and wires.
my guess is spark plug problem or distributor box
First thing to do is replace the plugs and wires if you have not done so. It you have or if replacing them does not fix the problem then have a compression test run.
try accelerating slowly. if it doesnt stall, you may have to keep accelerating slowly[until someone else can diagnose tyhe problem]
antifreeze is most common problem related to petrol engines misfiring. this can be cured by replacing the timing belt in addition to the thermostat and coolant temperature sensor. this will remedy 95% of misfire problems on most modern cars.
Most common cause of that is, Bad spark plug/plugs or plug wires, I think you will find your problem in that area.
check the connections behind the gauge they could pop loose
i have a 2.0L 2000 jetta and it did the same thing, I had to have the throttle body and 02 sensor replaced.