I'm gettin ready to place my order and get a Boost, EGT, and Oil pressure guage and it's asking me if I want to purchase a pressure sandwhich adapter with it for an extra $39? Can someone explain to me what this is. Also isnt $119 a bit much for a Autometer A-pillar 3 guage pod. Any other suggestions on where to get a guage pod like that a bit cheaper? Thanks for the help.