'Using silicon glue and plugging from the inside sounds like the safest method to me'
And I would say exactly the opposite. If you plug from the inside - there is always the chance it may come loose and be sucked into the engine
Whereas if you plug from the outside - if the plug comes loose and falls out - well, your car will simply run like crap or not run at all (due to increased intake air downstream of MAF).
But at least you'll know what the problem is and EZ fix - but if it gets sucked into the engine, not so nice...
Don't really see what all this infatuation with more intake noise is all about anyway (which is all this mod may accomplish). Sounds more like a 'Hey, look at me' mod
It's not like removing the silencer is gonna yield you anymore HP - which is all I would be concerned with.
If you want better intake flow, either in order of least to most expensive:
- Cut charcoal filter out of stock airbox & install aftermarket filter
- Swap airbox over to the Euro airbox with aftermarket filter
- Buy aftermarket intake
- Install BMW Performance Airbox & again, cut out charcoal filter