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