You dont need to pull the bumper to realign. Loosen the bolts at the top and the side and you have some room to move. However if the bracket under it is misaligned. But that's a lot of work to check if the bracket is off my a few millimeters.
Different materials will give you different reflections. White is one of the harder colors to match. Depending on the shop they might use different brand of paint/base coat. Lots of reasons why yours might not match.
I mainly want all the reinforcement bits that got added. The front cowl brace, half cage/brace and maybe the under side ones to if Cusco doesnt come up with replacements.
The silicone rings that join the the filter box with the tubes? Thats took some finessing around to get it to stay sealed. I dont mind that plastic rivets if it was to tight the ones facing the front bumper would be even harder to get in.
How much did you have to cut out? Size of heat shield or the AOS?
Engineer what parts better? I dont think its HKSs responsibility to make parts fit with other brands.