I know Umnitza sells the MTech rear and you can also order the quad diffuser from them. I was also considering it at one point. I imagine the other sellers have the same thing since they are all coming out of China. My recommendation would be to purchase both from the same source. This way the fitment should work the best.

 

I got my diffuser for the Mtec bumper from Eurorev a few years back. Its an oem diffuser that they modify into a quad setup. It took a little while to receive it once ordered, but the workmanship is excellent and the fitment is obviously oem.

 

We carry those Mtech bumpers with quad diffusers from time to time, if you want - we have a special order for another customer and if anyone is interested, we can add a couple to our next container.