Stumbling in 4th and 5th in high boost

[Wisecut]

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

 

[daitken5]

did you check for boost leaks

 

[Wisecut]

did you check for boost leaks

Yep did that to. Nothing there.

 

[Twistaye]

You should take a log and post it up here if you can, would help narrow down the issue. Maybe getting too much knock and timing is getting pulled.

 

[zachwilliams02]

Or he is hitting fuel cut or something like that. Check your alternator circuit and if you have a good batt. I remember I broke an altinator belt and it would hit fuel cut at like 4k rpm

 

[2gjlc]

I had a similar issue where my plugs opened up a bit over time and under higher loads /gear it would breakup under boost. Hopefully it's something that simple for you.

 

[Greedy Pimp]

Try a smaller gap, like .018, so pulls wot 1 to 3 fine but 4 and 5 it misfires? How old are the plugs and make shure the caps are tight on them because they will come loose. Every new spark plug I tighten the caps even more because that can cause that problem.

 

[Wisecut]

UPDATE

Bought some ngk br8 spark plug and gapped them at .022 prblem has almost gone completely away. Im going to take them to .020 and hopefully all beter. Thanks for all the help..