Hi Freelancer, I hope I haven't created the wrong impression here! No, no track days, just some spirited driving conditions permitting and the other half absent!!
I'm not sure if there was any specific problem attributable to individual components dude. The OE simply didn't work. There was no bite at all. Bare in mind they only made 4000 of these 12V Spiders and the calipers used seem identical to the 2.0.....When they introduced the 24V Spider/GTV cars in around 1996-1997 they immediately upgraded the brakes with 4 pot Brembos' and 305mm discs as far as I am aware. This is essentially the modification I have done. The specifics were initially dealt with as follows: Total restoration of OE caliper, Greenstuff pads, new discs, Goodrich hoses, new fluid. The car simply wouldn't stop adequately ( I'm not hard on brakes and compare more than well with most folks). It is worth noting that the OE disc diameter of 284mm was identical to the 2.0 cars....on the V6.
In short, they put the 2.0 brake system on a 3.0 V6 with identical chassis. Only the upright was redesigned, but even the offset seems identical to the 2.0 car. Enter our Greek friend Guilia GT, who has a car like yours.
At that stage I felt the issue was sistemic-The 12V V6 in the front with 2.0 running gear!! My 2.0 brakes I find adequate if running Greenstuff pads however. for normal use. Hope this helps.