1.9L Turbo off - eninge misfire's at higher RPMS

[Golf/Jetta]

1.9L TD, 97 Jetta
complete head rebuilt last year
no leaks nor oil missing/coolent
new injector's this year
glow plugs changed two years ago.
timing on the button
compression 390 - 410 PSI
no blue, white, black smoke

running with the turbo its fine @ higher RPMS but when the turbo's waste gate is opened (off) the engine misses at high RPMS..

i had the air box off during the winter months (conned filter) didn't misfire with this
then put it back on during the summer (K&N filter) and it misfires

what gives?
thought?

[Rabbit on Roids]

i think its probably a miss firing injector. my audi does the same thing above like 4000. real loud popping and it smokes..

[dankcorey22]

It may be the fuel. you dont have enough fuel going to the pump at those RPM's. To solve: Get a lift pump

[the caveman]

A lift pump is a band-aid. It's not really solving the problem.

[Aki-76]

i think itīs lda.when waste gate opened,boost go sini wave and lda get inaccurate feed.

[Rabbit on Roids]

wow, this thread drew a response from Aki, thats surprising. 

[Aki-76]

 

[the caveman]

Do you have a lot of bubbles at the fuel line. If so, replace your fuel filter and check all the fuel line connections.
Or as Aki-76 said, the LDA is not working or is not getting it's vacuum signal from the intake manifold. Is the small hose bad/disconnected/missing/collapsing from vacuum?