Bongo Fury

I seem to have a power loss issue recently. My Bongo is a 2L petrol. Bongo was serviced just a few weeks ago so all filters et al were checked and/or changed and in general the vehicle is an all round good egg. The prob is intermittant but seems to have developed a notable aversion to hills . I do release pressure on the accelerator if it gets sluggish but even if it drops a gear I don't always get a swift resumption of power. Wondered if I have a minor blockage somewhere? I'm off on hols towing very soon and I don't fancy getting stuck in the undulating terrain of my far-flung destination. It has also caused a few scary moments when pulling out a local busy junction and deciding to pause after a few yards!

Please keep any suggestions simple as I'm not mechanically minded.... thanks

Firstly, you aren't going to get a lot of useful answers with the witty title, may be better to get it changed to "Intermittent 2litre sluggishness" - just a suggestion
You say filters checked/changed, what filters were changed? if the air fuel filter wasn't changed, then get that done asap.
Are you getting any sort of smoke from the exhaust when it happens?
Was it happening before the service? if not, is it something that's been done with the service, worth taking it back to whoever did it?
could it be as simple as the pressure relief valve on the filler cap blocked? when you get the power loss, open the cap & see if it sucks a huge lump of air in, or try running with it off for a short while or with a new one in place?
Check the air inlet isn't getting blocked anywhere.

Thanks for the suggestions Missfixit70. Will get these posssibilities looked into by someone who knows one end of a Bongo from another! At least I can give some pointers. There is no smoke that I am aware of btw, just from my ears when I pull out, the Bongo grinds almost to a halt for a few seconds and some impatient driver blasts me with his horn...