Caterpillar or Cat is what we call them, or is this a Chinese knock off? I had some boots like that once, "Gatopillar".
It sometimes helps to post the machine's serial number, it might be different than US machines.
Does it have visible smoke when the engine slows down? Have you checked the hydraulic filter for contamination?
This is a problem that could turn very difficult very quickly. If it's not a fuel supply issue, it could require an expert.