I was getting a lot of clunking noises with my delrin mount. In fact, when I first put it in, while the shift feel was improved, i hated it. I couldn't stand it. It drove me INSANE because it was vibrating like CRAZY at idle and would make these HORRENDOUS noises. I mean... i was so fed up with it, but I wasn't about to admit I wasted $100 on a product, and there was still the chance that maybe mine was defective or something.
So, I climbed under the car and identified the source of the clunks: I grabbed the mount and moved it back and forth / side to side a bunch and I could hear the metal inner bushing hitting the delrin outer bushing. So, I pulled out the mount, and with some help from speed3shon managed to place a small strip of duct tape on the outside of the metal bushing so that it sat nice and snug in the delrin bushing. Put it back in, wiggled it around, no more noises. Started up the car, and it was like night and day in terms of both vibrations and annoying noises. The car was just.... awesome.
However, after a bit the duct tape sort of deteriorated so I needed a more permanent solution. I went to autozone and picked up some 5 minute epoxy, slathered the inside of the delrin bushing with it, and put the metal inner bushing back in. So far, its held up really well, and this solved ALL of the complaints I had about the delrin MM.
Keep in mind that I'm still getting vibrations and rattles inside the car... thats inevitable, but the difference is that now they are a minor nuisance whereas before they were unbearable. And the difference when driving and launching the car is definately noticeable. Its definately a good mod for the money IMHO. I doubt you'll notice a big difference with any of the polyurethane mounts, they may help a little, but it'll only be a very slight difference. The delrin MM however has made a much more noticeable impact, of course at the cost of more vibs.
So its really up to you... all I can do is give you my opinion, and I honestly beleive that if you are gonna go poly, just get the CS inserts because the TRZ poly costs the same as the delrin and I doubt you will notice much difference between that and the CS inserts. The delrin is the way to go. Even if you only put it in during race days, its a simple swap to do.