2015 MUSTANG WILL HAVE IRS – MORE PROOF!!! Not a fan of this move personally, but we'll see how it works out. I'm sure everyone seen this yesterday, or even earlier this morning on Jalopnik. If not, here it is. Big thanks to Jalopnik.com for releasing these new 2015 Mustang “test mule” pictures. From the pictures you can clearly see the lower control arms of an IRS (independent rear suspension) system on this test Stang. You can also see the rear bumper has been cut/hacked up. It is safe to assume that this is to clear a redesigned exhaust system that has to be routed around the IRS system.