Need some suggestions please!!!!!

[Gill Welham]

I drive my husbands hilux surf (apparently it's a 3L Diesel) it's started playing up and we don't know where to start to fix it. After a short time the engine seems to loose power even when you don't take your foot off, will only rev to about 1000rpm. Then after 20-30 seconds the power will suddenly come back and it's back to normal. After the same amount of time it will do the same. Someone suggested the engine is going into 'safe mode' (my driving isn't that bad honestly!) Anybody got any ideas what it is, why it's doing about it and what we can do about it please. Thanks Gill x

[Koi]

Blocked fuel filter or blocked breather pipe on fuel tank. When it loses power pull over and remove filler cap do you get a hissing noise like theres a vacuum in the tank?

It does sound possibly fuel related, possibly the fuel shut off solenoid or accociated electrics?
Fuel pump or pump timing?
Also did you notice and white smoke from the exhaust when it does this as could possibly indicate air being sucked in to the fuel lines

Also could be boost problem, sensor on inlet manifold?

Has it been running on veg oil?