Hmm ok then...

Hey ripped off no datto master
ahhh need 1001 posts
2275 days of membership Im on here nearly everyday long live datsun1200.com

It takes 1001 I remember someone else being annoyed by this before

It runs fine at 8psi all the way to 8000rpm. But under load it misses. Is it missing above 8psi under 8000rpm?
The only difference is boost pressure reference to the ecu and msd dis4 (does it use a pressure reference?)
I would be thinking some limiter is being activated or wrong tuning setting. Both of which I am sure the guys at unigroup would have picked up on.

Fuel pressure is good and A/F ratio is good too. What is happening with the A/F ratio when its misfiring?
Silly question but where is the fuel pressure reading coming from? The fuel rail? or fuel line? Is the problem not something silly like a mix up with the fuel supply line and the fuel return, being mixed up between the regulator and the fuel rail?

RTFM?:
http://www.msdignition.com/pdf/6211_6215_frm23729.pdf

Is it possible you've knocked some of the tuning switches?

if it's not electrical, map sensor? your not running a AFM?

Sounds like a problem I had after 6000rpm under higher boost - turned out to be 2 things: 1. too large a plug gap (running 0,6mm now with a MSD setup. 2. rotor phasing.
I know your engine doesn't run a dizzy, but check your crank angle sensor (trigger angle) and if you've set it up for rising or falling edge trigger, and the coil charge time. Mine also felt like the engine would lit a rev limiter.

Well after much pulling hair out ect I finally fixed the datto. Steve AKA phunkdoktaspok
was spot on with the fuel pressure reg being hooked up the wrong way and when boost came on the pressure reg would go a bit spastic im so glad it was an easy fix.
Its off for dyno next week so I cant wait to see what 20+psi and a tune will make it go like.
Tonight with stock boost and mild tune it bloody hammers.
Thanks for all the input.
Cheers Andrew

Thats awsome news dude. Glad it was an easy/CHEAP fix. Cant wait also to see the dyno results.

damn that.

I'm too, very happy to hear about your recent fortune. I have two new injector boards, got the ECu in my bag, and my ECU is now ready for action

I've got the info to configure the boost control ..the rest is merely a set of new tyres..after I discover 20+psi