think I got the air filter figured out. Point A to B is no problem, but throw a giant MAF in the mix and it becomes a challenge without ditching the 2nd battery or the snorkel.
when the camel trophy went from 200 tdi to 300tdi they ran into the same problem many of us have: how do you fit a second battery and a snorkel with this plastic box in the way? I worked around it similar to how safari snorkel did, moved it over and cut a hole in the side. I didn't like it, but it worked for my regular boring production disco. Camel trucks took a different approach. Since the 200tdi inlet went through the fender (there is a circular boss leftover on all D1s) hooking up a snorkel was no problem. The 300tdi solution was to use a defender air canister and inlet hose (esr3032) put the intake on the output and joined it to the stock turbo intake hose. This fixes the snorkel plumbing and 2nd battery problem. The LHD trucks have the hose rubbing against the master cylinder so I suspect they would go through these frequently if used as regular vehicles. They also don't have the ABS modulator in the way. I ditched that a long time ago, so I've got room for this setup.
The plan is to recreate the 300tdi canister mount on the fender, use a spectre 3" elbow with a 1.5" CLR so no space is wasted, a mandrel 4" CLR 90 from that to the metal MAF connector salvaged off a RRC canister (same end as a NAS 90 and pre facelift disco) then flex ducting to take it from the MAF to the plenum. It'll sit on rubber isolated pegs like the RRC setup and ideally a QD tube clamp so I can change air filters without tools
The flex duct that rover uses claims a 30mm CLR, but the supplier molds the cuffs to the hose so its no something I can easily assemble at home. I'm going to be using the cheap spectre flex hose for now. I may get some of the flexflyte super (what I believe to be the rover OE hose supplier) and just silicone on some cuffs if the spectre stuff ends up being poor quality.
It fits in theory, barely, but it should get the job done.
I also think the flex hose from a 98 v8 defender (which I believe superseded the molded NAS intake hose when supply ran out) would work, but the plenum cuff is the wrong ID for the bosch.