This cam has outperformed any cam we have tested it against to date, from idle to 4,200 rpm. It is also the largest drop-in cam that we sell. It works well in a 4bt application for this reason. 4bt's usually have issues spooling turbos due to their limited displacement. For best spooling, use the 188-220-109 LSA, keep your timing conservative and use a 17.5:1 -19.5:1 compression ratio. A mild port job and larger valves can also greatly increase spoolup..Install intake on a 99 centerline, performance springs and pushrods are recommended. If you have had your head or block surfaced, you need to verify piston to valve clearance.For it to be "drop in" on a 8v you will need no more than .018" piston protrusion and at least .055" valve face depth with a standard head gasket and a 99 intake centerline. On a 16v you will need no more than .018" piston protrusion and at least .038" valve face depth with a standard gasket. If you do not meet the minimum requirements for piston to valve clearance, don't worry, you can still run an oversize headgasket or cut valve reliefs.Because the 4bt market is fairly small, it does not make sense for us to spend the money it would take to have our own cast billets made. For this reason, we buy new cams and then cut our grind onto them. If you have any special requests for custom 4bt grind, call us and we will get you in on the next cut list. Call for approximate wait time and cost.