samurai lugging down

my 87 Samuri seems to be having trouble with acceleration mainly in third and fourth gears. Not all the time, just sometimes. I lose about 1/4 of my accelerator in third to 1/2 in fourth. sometimes letting the pressure off the gas tank will help and sometimes it doesnt. Heat does not seem to be a factor because it will do it cold. Any ideas?

Hi,
I had this problem once...it was my carb. I sprayed it real good with gunk and it works great now.....
Dave

I had also faced the similar problem.

Cat converter....