first would lose power and will not go over 35-40mph, pull off road, turn off engine then restart it, no problem accelerating until it happens again-usually happens when slow down or stop. then today it did this and went to reset it but when turned on and take off now you hear like air leaking as if you had flat tire cause what i thought at first but goes away after get going
you can get up to speed just takes awhile but barely move when hit hilll any suggestions thanks ahead of time

(note) when investigate air sound is comming from passenger front but sounds ike comming from back of engine area
and my sprinter is 08 dodge 2500 sprinter diesel