Hi guys, escort large turbo, standard, has started being silly!

takes 5-6seconds to start up, then might die, but the major problem is when your driving, the car back fires and the rev counter goes balistic, bouncing up and down, you dip the clutch and it wont rev out, afew seconds later it stops doing it! does it at any random moment 20mph 100mph any gear, when car is on or off boost!

any ideas lads?

p.s its only done it in the last week, fine for 8 months. and it take longer to fire up.