Hi all: I bought the Kubota air intake assembly for the D850 diesel ($105.00 USD) last week. The hoses shown in Aaron's parts diagram are no longer made, so I made my own hose configuration by using three 90 degree, 1 1/2" Fernco rubber boots (Lowes or Home Depot, in the PVC plumbing aisle), and a 24" length of 1 1/2" PVC plumbing pipe. If you have a Cat 30 of the eighties vintage, there is plenty of room above the transmission in which to house the intake assembly. This DOES quiet the engine, but it is NOT dramatic IMO. The rushing sound of intake air is eliminated, but all the other loud engine-related rumbling continues. The stock air cleaner (with the steel wool and foam wrap) is worthless for eliminating the air intake noise, and the engine sounds no different with or without the stock air filter. With the Kubota filter unit, you WILL have a noticeable decrease in air intake noise, but not miraculous for overall quieting, at least not in my case. I'm now looking to new engine mounts and soundproofing to continue the quest. I just purchased some RAAMmat and Ensolite to line the settee enclosure with. I'm also considering creating a soundproofed "false wall" between the engine and the macerator pump area to eliminate some of the large cavity beneath the settee area. Any input on selecting appropriate mounts would be most appreciated. If anybody would like photos, I can provide them.