I have searched and searched to find the answer but still am unable to find out what's going on.

I have a 92 laser that runs like great 1-3rd pulls hard and no missing or stumbling. But if I am on a country road and pass in fourth as soon as I get to about 20psi it starts to fall on its face. I am running 27 pounds of boost and was dyno tuned. However they only ran it in 3rd so they didn't notice the issue. I also have put new plugs br7es gapped at .022 and wires. Neither has helped, just seeing where I should go from here. Also have done boost leak test.

Thanks in advance

92 plymouth laser rs awd lsd rear end.
103k
motor has been bored .40 over balanced crank shaft 1g rods
4bolt rear end
Act clutch
Tial wastegate
Blowoff valve
All hardpipes
Slow boy manifold
Megan exhaust 3" turbo back
fmic
Hks cams
Bc springs and retainer
Zetronics wideband radar and display
Intake. 2g maf
Weisco pistons all new gasket and seals 10k approx
Valve job
Metal head gasket. Arp head bolts
Pte 3431. Bb turbo
850cc injectors
Dsm link
255 walbrol
Fuel regulator
Turbo timer