leak test

Hey hundy folks. I’ve got lousy mileage suddenly on my 06 LX. Got the common 420 430 DTCs, new aftermarket cats, all 4 O2 “sensors” from Denso. Smooth start up, no misfires, no acceleration issues, engine SOUNDS great. But, cruising on the flat at 65mph getting 10 mpg, where I used to get 17 or...