PICTURE: SP Cover above with anti surge bullet holes. SC6162 650hp More bottom and mid range power SC6169 650hp SC6176 680hp More top end power Say your picking for a 2.0 Liter motor: .63 A/R Better for smaller displacement, quicker spool and bottom/midrage power .82 A/R Better for larger displacement, slower spool but more topend power COMPRESSOR COVER: E cover is a straight 3" inlet, larger type-S (4in inlet) or type-SP (4" inlet and ported with bullet holes for anti surge (Makes a bit less power then a S cover) The Type-E cover is a 3" inlet so its easy to find a filter or make a intake for. The outlet that connects to your intercooler pipes is 44mm as the SP is 58mm. Oil connection only if thrust bearing. Oil and coolent connections if ball bearing. The coolent kit is needed for warranty and needed to keeps turbo cooler for long lasting boost. 4 or 5 bolt downpipe flanges if T3, the T4 will be vband. If your manifold was built for 4 bolt or 5bolt its important to pick since the 5bolt is about 1 inch more "on center" then the 4bolt. Go with the 4bolt if T3 usually unless you have a reason for the 5bolt. If not sure what you want, list your engine size (1.8L, 3.0L or 1700cc ect) power goal in wheel horse power (450whp ect), and other info you think we need and we can have the turbo picked that best suites your needs.