Ok i'm starting to get really fed up with my trainers engine, in months I havnt had a successfull flight without a dead-stick or "bad sounding" engine necessitating an urgent landing.

It is a Magnum XL 52.

2 weeks ago I replaced ALL silicon tubing and secured them with small zipties (not too tight so I made sure I didnt cut the tubing...)
This was while trying to fix this problem, At that time I also found out that the needle valve (placed on the rear with a tube extender) outlet nipple was broken and letting air in.
The valve has now been moved forward and there is NO air in the tubing.

The plane always behaves perfectly on ground at startup etc.. but once in the air... things go wrong... it will "missfire" (not sure if its that but it hickups) or sounds very wet.. or just cuts out, on any throttle possition.

Today we started to work out that when we gave it full throttle... and someone picked up the plane, shook it.. moved it arround all axes, it would cut.

I'm getting seriously fed up and close to binning it and buying OS.
As its had a few "begginers landings" i'm wondering if its just taken one to many bashings..?

but where else can I look?