Runs ragged then picks up? Hijet 2005

The engine starts fine and idles nicely but when I change up gears it will run ragged for a bit then suddenly pick up! If I don't ease off and re-accelerate during raggedness it can sometimes cause a single loud back fire and even more rarely cause the engine management light to briefly flash.  Checking the engine I did find a thin hose pipe that had worked itself loose from a connection. I've reattached it but the problem persists. I noted the engine makes a snort gasp sound when I suddenly put down the throttle hard? But not sure if it always has done this?

Problem feels like an old fashioned advance and retard vacuum fault. Maybe electrical problem as plays up worse in the wet. I have checked the engine at night time but couldn't see any sparks.

If it needs specialist attention my concern is finding a local (Norwich/Norfolk/East Anglia) good mechanic/diagnostic technician who knows the Hijet. A few years ago I took it in for a different fault to a garage who had it for 3 months saying the computer said it needed to a whole host of things changed - it ended up being a simple broken spring in the throttle throat! I felt I was paying for the their training!

Hope forum can advise.  Chris D.

There is an expert, a bit North of you. Welcome, btw

PFM wrote:There is an expert, a bit North of you. Welcome, btw

Can this Northern expert be unmasked? Thanks. Chris

Highly Jetted in an earlier forum shows a "Ported Vacuum Switch" diagram.  Maybe this unit relates to my fault as this was where I originally found a loose pipe?  Where can I get one if necessary?