need help with power
 

hey everyone i'm new here but from what i understand this is the place to find answers.
i have a 1990 4runner sr5 v6 manual 2door (very rare) about 220k miles on it but about 2k miles ago i pulled the engine had it rebuilt and new transmission. new wires, fuel filter, oil change, air filter, and the afm test well with in specs, new muffler and pipes, also new oxygen sensor. did the self diagnostic and only thing that comes up is speed sensor circuit (even though it's a cable) but the old boy is still suffering up hills and accelerating with poor gas mileage. also had a shop pull the cat when they were replacing the muffler and they said it was fine but it looks almost hollow, not as dense with the honeycombs as i had suspected it to be. i'm at my wits end if i can't find out what's causing this i'm going to have to look at selling it. i'm in the military so of course money is a issue. i've spent our savings on just getting to where it is now. i understand the 3.0 is a little sluggish but it's to the point where i'm loosing rpms in 4th and 3rd gear. i desperately need a fix soon before i loose it

need some where to find a speedo cable.

also on a side note sometimes when i am coming up to a stop sign the rpms start dropping and will come back up almost if it's starting to cut out but comes back. it will go up and down untill i give it some gas and it will temp stop