my 2004 SX2.0 revs up to about 4k rmp when i start it while its in park and then drops down to around 1k. and when its in drive or idle it revs back and forth between 1k and about 1.5k... first i thought it was a vacume leak because i could hear hissing coming from near the throttlebody. but then i noticed i lost my power breaks so im wondering if it could be the pcm.

codes: P2074-manifold Pressure/throttle Position Correlation.
p1697 pcm failure sri mile not stored.

 

why can't people spell VACUUM?

probably a leak and if it's the main line to the power brakes, that will give you hard brakes and high idle.

 

It seems you've got spelling down. Try working on grammar now.