Turbo Boost
If you do turn the Boost up above 15psi then really the fuelling needs to be adjusted to pump in the correct ratio of fuel into the engine by maybe using bigger carb jets. If you do not increase the fueling to match the higher Boost then you will get "PINKING" or "DETONATION" as it is called. This WILL damage pistons which are expensive to replace as the engine has to come out and the engine be rebuilt.
A
0.55bar 8.25psi
B
0.65bar 9.75psi
C
0.7bar 10.5psi
D
0.8bar 12.0psi
E
0.9bar 13.5psi
Another cause of a head gasket to blow is the car overheating and considering that 5's run hot as it is there really is no margin for error. So if you're driving a 5 always keep a watchful eye on the cars temperature gauge. Driving along a five should read just below to halfway on the temperature gauge under normal driving conditions and maybe rise a little on the motorway and when putting your foot down where the Turbo is being used alot. While sitting in traffic the Cooling Fan should cut in just before the 2 3rd's line on the gauge. If you notice that the fan doesn't cut in when the temperature gauge gets to the 2 3rd's line switch the car off and let the car cool down. "NEVER LET THE CAR OVERHEAT" "NEVER LET THE CAR'S TEMPERATURE GAUGE GET INTO THE DANGER ZONE AND WAIT FOR THE RED LIGHT TO COME ON AS BY THEN THE DAMAGE IS PROBABLY ALREADY DONE" You may have a dodgy thermostat or Fan switch which isn't working properly which may be the reason the fan isn't cutting in.
FOR THESE REASONS THE CAR'S COOLING SYSTEM ALWAY'S NEEDS TO BE IN GOOD WORKING ORDER.