I have an 87 toyota pick up 4 cyl 2.4, It has no power going up hills the tires are one size bigger than the stock tires but I dont think thats what it is. When i'm in 4th going up hills it will drop to 35 and i've tried shifting down and it still wont go. Does anyone know what could be the problem?? Thanks (its also 4wd)

Very hard to say just from your description. Check all the normal PM stuff. Air/fuel filter, spark plugs, etc.

Your truck is 21 yrs old with probably 200K mi on it.
I'm betting the cat conv is the original and it's clogged.
That's one possible cause your symptoms.

could be the fuel pump, check the fuel pressure. ( not sure what it should be if its fuel injected, should 4 psi if its carberated)

I had a 79 toy with a 20r. It was reasonable on the hills until one day where it lost its ability. It turned out to be a cracked exhaust manifold. Something to check. Maybe a fubar cat converter.