Track 172cup
								
							
						
						
	
						
							
	
						
					
					
						
	
					
				
				is the ducting in the link below that i've seen a lot of people use smooth or ribbed on the inside ?
 
http://www.merlinmotorsport.co.uk/p....html?osCsid=f7ebc18a53c95a8beded3092e4faaaf4
			
			http://www.merlinmotorsport.co.uk/p....html?osCsid=f7ebc18a53c95a8beded3092e4faaaf4