Dear Pe,
First of all, thanks a lot for your prompt answer.

We have been working with MTW TD75, KS 88 VS-5 R canisters and eventually with Bison pits style. Propellers: Mejzlik 28x10x2 (6.300 rpm), Biela 28x10x2 (6.150 rpm) and Mejzlik 30x10 (5.850 rpm) in Madrid which is 700 meters altitude.

We should recognize that the H needle has ben set very slightly rich and the L needle to have the best response up-side down probably 25 minutes or slightly less. We will now work as per your suggestions.
By the way, I forget to comment you that in the first engine we had, during last summer, we checked the static pressure tube that we knew from your website but we didn't find any improvement probably due to the fact of our mistakes tuning the engine well.

Something about the big hose that comes with the engine?

We are going to follow your suggestions this weekend and I will tell you our experiences.
Thanks again for your help and best regards,
Andrés,