Intercooler on ANY turbo-charged vehicle is a BIG YES. You want optimum performance out of it, you intercool it, period. How you use the new available power is up to you. You can gain fuel economy if driven proper, or gain brute force, with less fuel economy if you've got a heavy foot.......like me...
The Isuzu having a weak turbo is a lot of hogwash. I've taken a 280 to 416 big ones and sold it in 2005 for the 300. That 280 is still running today in Durban and I can give you Morgan's telephone number if you want to confirm that. The 300 is touching 200 big ones with no problem on the turbo. About 200 active members on the Isuzu Offroad web site, most of them in 280s and I've not heard of a single turbo failure. Blown a motor or two, but never a turbo. Engine failure occurs for one of a couple of reasons, each one of them under the control of the driver.
1. Overheating due to no water..burst pipes etc
2. Leaking/worn out injectors due to lack of maintenance
3. Overfueling due to owner or unimformed person fiddling with the injector pump.
4. uninformed people playing around with turbo boost pressures trying to increase performance.
In the early days of TDs, which Isuzu started in SA, there were some failures, some mechanical, but the vast majority due to driver ignorance. There is a way to drive a TD, and it is different to a petrol. Once you got those under control, that turbo will outlast your engine, and on a 280 Isuzu that is a serious claim, and I stand by it.
Before you buy, have it checked out by a proffesional, and then take care of it. All TDs do need to be treated with due common sense respect, or it can cost you a lot of money, and the Isuzu TD is no different, just more forgiving than most, if not all others.
Some people say I have a "short temper"....I see it as swift and assertive reaction to Bull!