my 1986 "elmer" subaru 4x4 wagon chugging,carb problem...

idles ok but as it revs or accelerates around the 2k area fuel cuts off to almost nothing , and jerks and chugs really bad like my cables or distributor cap or rotor or bad , but they aren't.

i have floor it and let up over and over to get anywhere

the problem also comes and goes

i also noticed that i couldn't see the secondary jet come on unless i push the flap open with a screw driver

any help would be great

thanks!