I read multipul places that you can increase MPG by removing the MAF screen aka restrictor plate. On the 4.3l v6. Is that true? I also heard it could cause some trouble too. But does the benifits out weigh the down side?

 

If you remove the restricter baffle it will increase throttle response. Thats about it.

 

The MAF screen won't really change anything on your engine... Not noticably, anyway.

It's there to smooth out the air flow from the stock, paper style/low flow air filter.

The restrictor plate on the TB will improve throttle response, but on earlier EGR equipped trucks, you'll have some combustion issues in the front 2 cylinders.

 

Regardless of the intake arrangement, the MAF screen is there to smooth the airflow through the sensor. Any twists/turns in the intake path before the sensor will result in an unequal flow velocity through the sensor which can skew the airflow reading that the PCM uses for operation of the fuel system.

On the throttle plate deflector, I had done this mod to my old Bravada and it made absolutely no difference at WOT performance, but did increase the initial throttle response. With the deflector completely removed, I was starting to see an uneven AFR front to back as evident by reading the plugs. I attributed this to a higher concentration of EGR gasses being sucked into the front cylinders, displacing fresh air, causing a rich condition (too much fuel for the O2 in the cylinder) on the front cylinders.

I was going to experiment with a shorter deflector to see if it would correct this imbalance, but I traded the truck in on my Rainier so I never got the chance. I was going to try a 3/8" tall deflector, as found on the 5.7L throttle body as opposed to the 5/8" deflector that comes in the 4.3L TB.

 

Has anyone grabbed a 5.7L throttle body and thrown it on their 4.3L? If so what was if any the outcome? And what would be the appropriate model years to salvage a TB off a 5.7L for '01' and newer 4.3Ls?

 

I thought the TB was the same for the 4.3 and 5.7?

The 5.7 gets the smaller restrictor plate, because it sits more in the center of the engine compared to the 4.3...

I think that's the only real difference between the two...

 

Sorry should have clarified that. I meant for purposes of the deflector plate only. I know they are the same size.

 

You can just grind down your current deflector plate to the same size as the 5.7 one... I think it's 1/2 theheight of the 4.3 one...

 

Any '96-'02 5.7L throttle body can be used to pull the plate from, or just use the whole TB as there are no differences between the 5.7L TB and the 4.3L TB aside from the deflector plate. The plate on the 5.7L TB is 3/8" tall.

Basically, given the location of the TB on the 4.3L engine and knowing how & when the EGR system operates, you want the deflector to be tall enough so that it partially directs the flow of air off the back side of the throttle blade during normal operation of the engine (i.e. cruising).