the xz is a whole different animal than an OS SPEED or a Vspec .21, The OS 2050 and 2060 are different than the tuned pipes for .28 engines.
Per the OS site:
The Mark Pavidas Edition Tuned Pipe (OSMG2969) is the perfect accessory for the 28TZ
I am not a fan of the larger .28 motors, save for that the power delivery on the low end is very controllable and torque filled, which works well with a corresponding clutch setup in a truggy. By running a 2060/2050 you are likely losing out on some power that a pipe built for the engine will give you. I mean that mostly you are losing out on the bottom and mid range grunt that the .28 will give you, or making the motor peaky and only make power at top end. This is a bigger deal than one might think, if you are able to control it.
If you don't believe me, the thing to do is switch pipes with a friend for a day.. it makes a difference.. mostly in power range.
Your best bet if you are not going to use the Pavidas pipe, would be one of the Jammin JP1 or JP3 pipes, which I have seen work well with the LRP .28 engines.
my two cents.