Reduced power, shaking, wont change gear

Okay so this truck has been the bane of my
existence since i got it. A mony dump when
it comes to this problem and im not doing
anything else till i can get some way to
diagnosed the issue. About 3 weeks ago I
get home from running some errands and I
cut the truck off. About five minutes later I
realized I forgot something so I hop back in
and started up I go in reverse, reverse is fine
and then as soon as I get out of my driveway
I press the pedal down, it sinks to the floor
and refuses to go over 2000 RPM. Now keep
in mind it doesn't have the issue its on and
off it doesn't always do it. But it has gotten
worse. So I was thinking it might be a
clogged fuel filter I change that then I was
maybe thinking you might be starving for
fuel changed  the fuel pump. Same thing.
Then it started misfiring at idle or at least it
feels like it's misfiring. I'm not confronted
with the issue when I have the reduced
power  and hit the brakes and I get down to
about maybe seven eight miles an hour the
truck starts shaking horribly it feels like it
wants to die but it won't. This is only when I
apply the brakes and the reduced power is
happening. Also take a long shot in change
the throttle position sensor that wasn't it
either. Now before you guys say cats keep in
mind this truck Has none it's just straight
pipe. Again it only happens maybe every
other time I start it up if it's a cold start it will
run fine. I was dealing with the problem  I
can still get on the highway I can get it up to
speed I got it up to maybe a hundred without
an issue. I hooked an obd up to it as well no
codes came back. Does anyone have an
idea of what this things problem it?