i ran a fmf ram valve for years in my 88 500. tried a stock cage one day with boyseens and it ran better. felt like it had better throttle response. now i have v 2's and those run better than the boyseens. if they were any good you would think fmf would still sell them.
87 fmf ram valve actually has less surface area than a stock cage. cage is the same as the 88-92 but with the correct bolt pattern