The inexpensive replacements can fit like garbage. The factory stuff is always better.

If it is stainless steel you can clean them well with Castrol super clean. Clean one at a time, use on a dry surface, let is sit a few minutes, don't let it dry, agitate with a toothbrush, rinse. The tar will be left behind, but much of the grime will be gone. Tar comes off with carb cleaner or gasoline. If you need to clean it again get them dry, water will not help anything.

If they are aluminum you must be careful with the Casteol super clean, it will eat the finish so spray it on and start with the toothbrush and rinse before one minute.