Replace those tie wraps with these spring clamps that maintain continuous tightening on your coupler. Pliers spread these to about 1 1/4 inches and close to 1 inch.  We use these on couplers with a 3/4 inch ID. We use the 29mm for pipe side where coupler is pressed over the tuned pipe. Makes your material last longer and makes for a tight coupler to header/pipe contact.  The result is not letting exhaust gases to leak, thereby maintaing good horespower.  These are far superior to ones you might find at McMaster and are much more user friendly.