monte carlo missing 2002 ls

i have a 2002 monte carlo, driving on the road it stoped running, wouldnt start, when i got it home it started but missing bad, i replaced the plugs and coils, didnt stop, tho one seemed to make it a little better, strangely i have noticed the power brakes dont work anymore, very stiff like standard, so may be connected as happened at the same time, searched for a vaccuum line off, dont see one......any help or similar situations??

1) Did you check the belt tensioner bracket?

2) Failed head gasket?

I have worked on a lot of 2001 monte carlos with this problem these cars were built in canada during winter and when they are out side the batt.freezes and drips acid all over the 30 pin elect connceter and eats thru the wires.check this connceter for damage from battery acid.