I've got a 99 Silverado that has been swapped with a 6.0L LQ4 with a 228R cam and supporting bolt ons. I'm getting ready to swap on a TBSS intake and 90mm throttle body and currently have an Airaid MIT tube with a K&N in the stock air box. At what point does the stock air box become a restriction on these engines? Has any body done any testing or have any before and after input for a higher HP situation through the stock box?

 

I have nothing for real data but all you have to do it cut the stock box open more.

Make the whole side open and drill a hole or two in the front and it will have all the air flow it needs.

 

I've read the stock airborne can support 700ish. Having said that, I have made around 630 crank hp with a stock airborne and drop in filter

 

This comparison was done on another site back in the day. Cai Dyno Wars Results - Bolt On Performance - SilveradoSS.com

From top to bottom on the horsepower curve on the graph is:
AEM no filter
KNN
AEM
Stock with KNN drop in filter
Outlaw
GMPP
Stock with Fram airhog

 

Also Found this one done by justin of Black Bear Performance.

 

I've read those data sets before and understand that the stock air box performs well with the addition of an airaid MIT and K&N. Which is why I have run the exact combination up to now. However, all of that testing has been done on relative stock trucks with smaller displacement engines. And that is what has me wondering when that combination begins to loose efficiency and become a bottle neck. I suppose that I can measure my KPa once the new intake and TB are installed, that would be the definitive tell all for my particular application.

 

My 05 Silverado came with a K&N, and I just added the Airaid MIT. Noted that the TC stays locked further up the hills around here, slightly peppier feeling taking off. But it also gets LOUD easing past about half throttle and feels flat....HPtuner showing knock retard kicking in.

 

The perceived power difference most feel and swear by from changing out the stock box to aftermarket CAI is just the effect of leaning out the factory tune.

Stock boxes flow very well for the most part any gains to be found are in the box to throttle body duct.