my s max has developed a fault started in 3rd gear when reaching around 3000 rpm it will kangeroo cut out start ect and will not rev round past 4000 rpm its now happening in second revs fine in first and when not in gear im puzzeled its almost like some 1 pressing the brake on and off

Check the wheel speed sensors / ABS sensors. If they're giving false readings the car will "cut" power to try to rectify what it thinks is a lock-up / slide.

hi how would i check these not showing no faults up on car but i have just had a clutch fitted 1000 miles ago and it has slowly gotten worse since then

changed fuel filter on a whim and it seems to off solved it