iv had burnley powerflow fit the zorst to my valver...bout 7 years ago...until the guy who bought it off me wrapped it up 2 years ago, was still all good on the zorst front. was also one of the quickest valvers around at the time, on these very forums...albeit RSC then.
the one on the williams 0159 has been fitted for 5 years now..never had any trouble with it , or powerflow, and theres not many that are as quick out there with same, often more mods. this is on 3 diff engines also btw, so not a 'freak' lump.
williams 0051 will be going there for a system soon.
chris n nics cup went there.probably the quickest cup around for quite a long time
monkeys williams went there, which took the 1/4 time record off mine.with same mods.
results speak volumes.
whether its bent with mandrel or not...they work better than most in terms of on road speed.