Thanks for your answer Would I be right in assuming that we are dealing with negative pressure here ie suction therefore the wider the opening the lesser the vacuum at the guage ? I have a spare brake booster hose so have some room for experimentation, how likely is it that by drilling out the tee section my reading will reduce, what size drill bit would you reccomend? as far as the locking secton goes the yellow valves are non return right ? so with minimal leakage on that side the resevoir will fill and stay full enough of vacuum to still operate the locks regardless of the desired drop in vacccum for the tranny ? as concerns the needle valve suggestion I am not sure where to get such a device, does this act as an extra bleed or is it just a tap which increases the vacuum when locked down,Would a syphon tap such as you might use for beer making work? again I assume the smaller the gap the bigger the increase on the guage, look at me I am writing very long sentances now thanks again

Felix