A stronger diaphragm than the shite worn stock item. It'll build and hold boost a lot harder. There is a boost restrict in the hi/lo module that you can bypass to give you full boost in first and second just by looping over a wee pipe! But honestly do yourself a favour and rip it out. Low boost is for pussies! I've a mate like you, He decks all of his cars! He had a mk2 golf we used to call the snake. because it slid along anywhere it went on its belly haha!