timing tuning problem

[filh]

I broke the engine two times this year , and the first time , timing advance was the reason .
My machinist prepares many races engines and he told me that on Opel AStra, Citroen Saxo, C2 , Peugoet 106 , at 6000rpm ,he never put more than 30° .
But , of course, he tunes the car on Dyno . But infortunately, I got no time to make the Dyno test , as my next race is on Sunday .
AS he set the timing on 3° at idle (T&E1 jumped) , we had 29° Timing advance at 5500 rpm .
But when I drove the car on road ,I found it much too slow , with a leak of power .
I've now set the timing at 7° at idle (T&E1 jumped) and it's now much more drivable . But the engine has only 200km and must have some more km to have a realistic try .But I will not have much time to do them!!
I'll try to remove the vacuum hose , but I'm not sure of it :
Is it the hose that goes from a black box(vacuum sensor) near the chassis number, to the intake manifold ?
I'll try if there is a change in timing advance by disconnecting it .
I forgot to mention about my mods , that I have a 0.8mm head gasket .
So the volumetrical ratio is higher than stock and may requires less timing advance ???
Thanks for helping
Phil