Generation IV External Engine - vacuum hose beside horn?

This hose has come undone and im trying to figure out where it goes.....

horn fluid

There's a vacuum canister under the passenger side frame rail that it goes into. Only one nipple on the canister you can't miss it. This helps control the HVAC system and blower doors etc.

yep, vacuum canister.

Well i took out the A/C. Im only asking this because my power brakes are shit now after my MS4 upgrade and wanted to know if hooking this back up would help...any.

no.. the brake booster gets its vacuum from the intake.. either you need to bleed the calipers or check the seals on the booster/master cylinder.. never heard of issues with the MS4 and low vacuum for brakes but who knows

so your pedal is hard now?

hook a vacuum gauge to the engine and see what kind of vacuum you have with the MS4.

If the pedal is hard your not getting enough vacuum to the brake booster.. If it is too soft bleed the calipers or you have a fluid leak. Common places where vacuum leaks occur are the "L" shaped nipple thing that plugs into the brake booster and anywhere along that hose to the back of the intake. Also the plunger that comes out of the brake booster into the master cylinder there is a seal there as well. Places for fluid leaks are the 2 o-rings on the plastic fluid reservoir attached to the master cylinder and any of the fittings/bleeders/rubber lines.