I had a similar problem with my RS1800 when I fitted my Bailey breather ( no fault of Bailey Motorsport as it was a new design that I was trying out for them as it was a 1st for a Zetec breather for them )..... Basically on the front of the Zetec block where the breather comes out on the right hand side (near thermostat) theres a 1 way valve.... I removed the valve when fititng breather and at Castle Combe (1st outing with new breather) it blew over 1 litre of oil out in about 5 laps (less than 10 miles).... I put the 1 way valve back in and since then it has used 0 litres of oil including Bedford on saturday.... This may help it may not


Steve