It's hard to say, but I'll bet he bored it without the main bearing caps torqued down to spec...the cylinder walls on a 7M are on the thin side anyway and can be distorted when you start torquing on it.  Especially when you go to the larger oversize bore.  Make sure he uses a torque plate and the timing belt tensioning pulley is torqued down to spec too.
			
			 
				
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		