I've been told to invest in a cometic head gasket for reliabilities sake. Now why on earth would I want 2 or 3mm whats the performance difference? What would you buy if you had to do it again and why? Also, whats the stock thickness if anyone knows that without me looking???

thanks guys

prepare for more turbo noob questions prior to my car going boost, kit is in the garge just collecting some last few parts

 

i first ordered the cometic 2mm and then returned it. i want the 3mm for the safer compression and pushing more boost. i'm gona go inline pro. im not sure on stock thickness. the 2mm lowers compression to about 10 to 1 and the 3mm is 9 to 1