ok basically i melted a piston 6 months ago,my mate has just rebuilt the engine and dropped it back in,car starts up,but it seems to hesitate/miss and hold back when the turbo kicks in,which is exactly what happened before it went bang,so the problem is still there,

so do i have to first run the engine in and then take it to msd to get it set up and looked at or take it straight there to get it sorted? or does it need to be run in 1st? i dont want it to go fooked again so can someone point me in the right direction,STU?any ideas what the problem is?

any advice much appreciated