Dump valve problem

[fuzzynuts]

Hi all I fitted my new type r dump valve but I seem to have a problem with the vac pipe for some reason if its on the valve it cuts the engine out I've had it off and flipped it around and still doing it so for now I've took the vac pipe off (valve sounds so much better with the vac pipe off) any thoughts on what's going on and is it going to damage my engine with it off

Thanks all


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