While you are waiting around remove every ground you can find, clean both ends of the grounds so they are nice and shiny on both the lugs, bolts, mount points then put a dab of dielectric grease on them and put them back on. Might want to stick a meter on those wires too if they are covered in insulation, they can corrode under it and you won't see it, the braided one can also be replaced for a buck or two at the store.
As far as finding a vac leak in the engine compartment, some carb cleaner or WD40, when you hit the leak you will hear the engine idle change, you can use water too but thats a bit more subtle.
One other thing, the OBDII stores the running parameters in there, if you replace a bunch of stuff it's a good idea to disconnect the battery and let the ECU reset to factory. Then reconnect and go drive it for 45 min or so, don't just let it idle and relearn, drive it. I had a big hesitation problem after I replaced my engine with a jasper, for 2 years it had a really annoying hesitation on acceleration, modis did not show it, nothing turned up. Back in January I had to replace the alternator and the battery got disconnected so the ecu had to relearn, the hesitation was gone. When the engine was replaced all they did was idle it and take it for a 10 min test drive then parked it. It never really learned it's parameters other than idle and short drive.
