Headers hitting idler arm
Remember that TTI does build an excellent product. But they don't build the car or the engine or the mounts and they don't install them. That leaves a lot of variables on the table. TTI does give you the dimension charts for the different chassis models and engine sizes for you to verify Before you install their product. It is in the directions and on their website.
Cutting, grinding, washers yada, yada, yada means something is not right, it doesn't mean you have to do those things for the product to fit unless it was defective in which case that is what the warranty is for.
Footnote #39