i change my buddy passenger side exhaust manifold gasket on his 2001 mustang with a 3.8L and now it has a rough idle. i had to disconnect the mas and the map sensor and egr tube. Then after i reconnected all the sensors and tube it has a rough idle. the only time it has the rough iis when you hit the brakes. it jumps around from 600- 900 rpm when braking.i was wondering if anyone had any ideas?