Turn right, skips and jumps, turn left, back to normal, what thehell?

I've got a weird issue with an 87 Toyota Pickup 2WD 4 speed pickup,
clutch has been replaced and transmission appears to be in half-decent
condition, but whenever I get going up to a decent speed the truck
will start to lose power, like skipping almost, if I floor it it'll
get some power then the moment I let off and try to put it back down a
bit theres no power whatsoever and usually I hear no change in the
engine when I put it back down. I'm not sure if its the engine or the
transmission or what, but I'm pretty sure its the engine. Also, if I
turn to the right when it starts to do it, it skips more, but when I
turn to the left, it seems to 'catch' and get power until I start to
move right again. So weird. Any ideas?