Removal of Pre-Cleaner on a GQ

Think not, but I wouldn't be too concerned.
(I removed my precleaner from my TD42 many years ago- amazing improvement in power and much less black smoke. The original setup was FAR too restrictive)
The water removal you were talking about is only for a dribble of water.... rubber orifice smaller than a 5c piece.
If you ever got enough in the inlet to cause hydraulic lock then such a device would make no difference.
Engines can actually handle a significant amount of water (eg: steady heavy rain whilst running )
If you were fording a creek and ingested a lot with the engine running, IMHO nothing would save your donk...

Linga Longa, we have a 1989 Ford Patrol / Nissan Maverick TD42, and it never came with a primary air filter, just a "dust spinner" (an empty cylinder with a dust removal hole at the bottom). So I wouldn't be concerned. If you do a bleep load of dusty work certainly consider putting it back in, but mind you we have been north of Birdsville with ours, in some pretty heavy bull-dust and never had a problem. The trick is to either buy an after market foam/oil filter and keep it regularly cleaned or clean (even replace on the road) the standard one frequently.

I've done it... it is easy as hell... Pipe from Purple pig... $20..

I noticed no difference what so ever in power and torque though even with the turbo

the bit about water, if its pi$$ing down rain, turn the snorkel head around backwards..

Also where the snorkel and the pipe to the airbox joins, there is a 1in high lip. The water will go here and not thru.. It shouldnt rain that much to hydro your donk....