after replacing my map sensor with a 3 bar one to cure a missfire,i seem to have got a new problem!

on boost after a certain time,i get a slight thud noise from under the bonnet and the car will lose power and not run to great.

by the time i have nursed it to somewhere safe to stop,it will cut out,get out lift the bonnet to see if anything obvious is amiss,get back in the car ,it will then start and run normally !!

the spec of the car is,3 bar map sensor,greens,exhaust,filter ,actuator,and pectel management.

before the map sensor replacement the car would not do this,leads,cap plugs etc all check out fine.

any ideas guys?

cheers