Just get the large diameter silicone/teflon extensions that are actually used for couplers for between a header and a tuned pipe. They will slide on and never come off unlike the extensions you zip tie on and they are clear and harder to see if that matters.

Something similar to this is what I used. My hobby shop had several diameters in 6" lengths for like $4.00 - put them on and cut them to the right length etc...

http://www2.towerhobbies.com/cgi-bin...?&I=LXJF43&P=0