a m8's just called and said his car WONT drive

he's just changed the turbo(standard t3) and fitted a (brand new) t34 to his 2 w/d saf car was running fine prior removal but NOW it wont pull away(wants to stall when trying to pull away) ticks over just about, says it's sounds like it's popping and banging out the exhaust

will pull away in reverse thou!
### he has rotated the housing for the actuator and thats it all### if thats any help.
one other thing:
HE'S DOING ALL THIS IN A CAR PARK OUTSIDE LAKESIDE RETAIL PARK