why when driving at 60 to 70 does engine start to loose speed and stall

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problem of car stalling and now this power loss after having work done to the tune of over $1900.00 never had this before they replaced, intake sensor,exhaust sensor,front brake sensor,control arm bushing,205/55/16 something???/regulator and more, all so engine light would go off and pass inspection. this car never stalled out and never ever lost power as it was being driven at a speed over 65 . this is the 3rd time since this repair i have had to bring this auto back. i am out of money so i can't even bring it to a bmw dealer, which i should have done to start with. help! what are my options?????????????