ORIGINAL: swartlkk

I have modified mine over a year ago. I'm more worried now about the uneven burn I'm seeing on my plugs. My front cylinders look to be rich (dark plug) while my rear cylinders look lean.

Other than throttle tip in (increased throttle response for light throttle angles), I don't feel that this modification did a thing. I just cut off the deflector with my dremel. Took me more time to clean my TB while it was off than to remove it, cut the deflector, and reinstall it.

I'll be going back to stock and looking for the 3/8" tall deflector found on the 5.7L throttle bodies. The primary function of the deflector is to promote the even distribution of the EGR gasses in the intake manifold. Without the deflector, a much higher concentration of EGR gasses will flow into the front cylinders causing incomplete combustion.

But hey... What do I know.

How EGR systems work The EGR valve recirculates exhaust into the intake stream. Exhaust gases have already combusted, so they do not burn again when they are recirculated. These gases displace some of the normal intake charge. This chemically slows and cools the combustion process by several hundred degrees, thus reducing NOx formation.

The design challenge The EGR system of today must precisely control the flow of recirculated exhaust. Too much flow will retard engine performance and cause a hesitation on acceleration. Too little flow will increase NOx and cause engine ping. A well-designed system will actually increase engine performance and economy. Why? As the combustion chamber temperature is reduced, engine detonation potential is also reduced. This factor enabled the software engineers to write a more aggressive timing advance curve into the spark timing program. If the EGR valve is not flowing, onboard diagnostics (OBD) systems will set a code and the power control module (PCM) will use a backup timing curve that has less advance to prevent engine ping. Less timing advance means less performance and economy. Do your customer a favor and fix those EGR codes that you may have previously deemed as unimportant.

ORIGINAL: swartlkk

What more do you think there is? Sure, you could richen up your mixture, but try to get too much hp and you'll quickly go static on the stock injectors. But then you'd loose any sense of decent fuel mileage. For the purposes of a DD, you'd have to reach a happy medium, but you'll get the best performance on a stock engine with a working EGR system.