RPMs shoot up while driving

renetta

2005 Mazda 3 that has had the engine and transmission replaced... while driving the rpms shoot up to 6000, sounds like the car is gonna explode, as soon as I tap the brake the rpms return to normal... Neither the place that did the transmission work or the ones who did the engine can figure out the cause... any help??

ray80

I might wonder about the throttle position sensor, can't say thats it, but I would wonder.