I searched, but could find no evidence of anyone measuring per cylinder A/F on a header equipped VQ. This whole plenum, air balance, unichip talk is seems to be based on O2 analysis by a single post-cat tailpipe dyno sniffer. The only real way to know what it happening is to install riv-nuts on each header pipe and hook up a multi-channel Exhaust gas analyzer. If the front 2 cylinders are "air starved" as Crawford and plenum guys claim, then we should see a measurable rich condition on the front 2. Unlikely that Nissan in this age of environmental, fuel conservation, and HP marketing wars would allow 33% of the VQ to be rich. Maybe they have compensated the fuel map to lean out the front 2. Who knows? But until I see real data from each cylinder, I dont believe that the stock VQ airflow is unbalanced. Just my 2 cents. Anybody want to volunteer their header equipped motor for some sample ports to be installed?

 

You might want to voice in this thread. The spacer thread. You may have a handle on what is going on. I also agree that stock VQ iS DIALED IN/.

 

Factory engineers have used special sparkplugs with built in pressure sensors to measure the peak and waveform of the BMEP through the combustion cycle for 10 years.

http://www.sensorland.com/AppPage013.html

Many times if you sell aftermarket products you look for the tiniest most minute variances and create [imaginary] problems where none exist to sell your wares.

If anything all Nissan engines are way way way over rich WOT to cool the heads/pistons/combustion chambers.

A 5% [even 10%]variance when beyond 12:1AF [as long as all are richer than 12] won't matter much in power output. The piston crown will be a different temperatures and thus the speed of combustion will vary [and the ignition advance might need to be optimized but over a 1-2 degree shift in point of peak effective pressure [14-16 degrees after TDC] the power changes are minor.