you are right to chase down vacuum leaks first - unless the system is tight, you'll be chasing your tail trying to adjust things that may be just fine...

i would suggest replacing every hose under the hood that's more than 5 yrs. old for several reasons:

- vacuum hose is cheap

- tiny cracks from dry rot are hard to see and can open up when you move/flex a hose that looks fine

- dry/hard hoses don't seal well at the fittings

- a bunch of small leaks can add up to a lot

be sure to check the pcv hose underneath the manifold - this one gets a lot of heat from the exhaust manifold and can disintegrate. also check your vac advance and fuel pressure regulator, as they have rubber diaphragms that can fail. another hidden spot is the rubber flex-boot between the afm and the throttle body - cracks can hide in the little valleys and may be on the bottom of the boot where you can't see 'em.

not all the hoses are the same size/diameter, so you may want to cut some 1" pieces off a few of them and bring them with you to the parts store - be sure to measure the cut end, not the enlarged end that is stretched out from the fitting.

and replace the hoses one by one, referencing the fsm for proper hookup. it's not uncommon that they are hooked up incorrectly (especially by a mechanic who uses zip ties on fuel pumps).

a/c tensioner tip--- the nut on the pulley is the lock nut. 14mm wrench then you can loosen the belt.