Hey Crazy,
The later Mass-Air 5.0s, not speed density (87-95?), gained a few horses from removing the air silencer. This was from the increase in air flow into the induction system.
The air silencer on a 4.6 is located in between the air box (where the air filter lives), and the passenger side fenderwell.
It is easily taken out, but I have yet to see any proof that this does a darn thing for the modular motors. Anyone can plainly see that its missing too...
You may gain more air flow, but you're sucking in hot air from the engine compartment. A plus here, a minus there.... You can try it, but I've seen no evidence that it does anything.
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Adam "Hammer" Packett:
Moderator, Gulf War Veteran
GO GET 'EM BOYS! 