Recently Ive been having loud, echo-y hollow exhaust noise and have subsequently noticed a lack in pickup. Its a 3.2 L v6 190 hp
5 spd transmission 96 Passport-and has been in the flat lands of NJ until now, which is taking on the hills of Washington state.
Now, I didnt have this excessive noise and lack in drive until I got to WA. I dont know if that could have anything to do with it. It is riding rougher in general, but the loudness of the truck now makes me think theres a connected problem.
Anyone have any ideas?

I would start with inspecting the exhaust system for holes.

I could be a baffle that has let loose in the muffler.

since you mention lack of pickup, it's possible you have an exhaust restriction. try holding a bunch of rags in at the pipe end (for a short time) and see if you notice 1.) a decrease in power (you should) and/or 2.) an increased exhaust noice which should indicate your exhaust leak which will be easy to spot if two of you work together one at the pipe end and the other under the truck.

what altitude are you in WA ?

it's possible it has something to do with the MAP sensor which also has some barometric reading duties (altitude), and if you are at considerably more altitude that may be the problem. did you drive across country, what happened in the rockies?

finally, even though i knew i needed catalytic converter replacement and muffler work too, when i thoroughly cleaned my "apparently" working egr valve, everything became noticeably quieter too.

//bc