ive noticed a plate on the butterfly when i open the throttle which effectively blocks almost a thrid of the TB, is there really a point behind this, or is it some kinda emmisions thing?

 

This same throttle body gets used on the 5.7L (350cid) v8 with no other modification other than a smaller deflector. The throttle body on the 7.4L (454cid) also shares the same casting, but with a larger bore and butterfly. The placement of the TB on the 7.4L is much closer to the center of the intake plenum than on the 4.3L and 5.7L. The deflector is there to direct the air flow more centrally in the intake plenum as well as to draw the EGR gases evenly to the cylinders.

With that said, I have run with my deflector cut off for around 8 months. The last time I pulled my plugs I was starting to notice a rich condition (unburnt fuel) in the front cylinders and a lean condition on the rear cylinders. I will be returning to stock as soon as I can find my extra 4.3L TB (moving sucks for keeping track of things!) and possibly trying out a 5.7L TB in the future when I can find one.

The only potential benefit of removing the deflector is to increase throttle tip in. Initial part throttle response will be better, but my scans before and after removing the deflector show no increase in WOT performance. Now things may be different if you open up the rest of the system (ie larger MAF sensor, less restrictive exhaust/intake), but I firmly believe that removing it all together is detrimental to your engine.

 

thanks, i believe you answered not only this question.. but all subsequent questions in the process