Another vibration thread

So I got my new rims. Exel TZ-10 18x7.5 with 225/40 Hankook H405 rubber. I did do a search on wheelmax, which did scare me a bit, but it was after the money went through. So I had to just hope for the best.

The rims do look awesome. But here is my issue.....

I am assuming that wheelmax did not properly clean the rims when they balanced them because the stick-on weights fell of in shipment.

So I get them balance at my local shop and throw them on with the plastic centric ring and cheap plated nuts that came with them. Everything looked good. Upon driving, I was getting a vibration in the steering wheel from about 90kmh to 120kmh (55mph to 75mph), the worst was at 120. It would disapear at 130kmh.

I take them back to my shop and explained the issue. They re-balanced again. Back on the road......no change.

So I investigated here and found a few tips. I go back to my shop and told them what I found, I said that they need to do a static and dynamic balance. My shop says that they tried that and that they have a feeling that it's not the balancing (of course) and that they have a feeling that it is either the centric rings, the rim, or the tire. They suggested swapping the front and rears. So that is what they did, plus they bumped the pressure up to 42psi.

I take it out for a spin. The vibration is only barely there now. Pratically negligeble. (could have even been the road at this point)

Upon talking with my shop after that, they are standing behind what they suggested the problem could be. They asked if I felt any rear end vibration now(which they said would be difficult to pick out unless it was really bad). I really can't say if there is any rear end vibration. At this point they suggested that I could try getting some better quality centric rings before going through the hassle of calling wheelmax.

Any thoughts? What should I do at this point?

Do I try better centric rings?

Should I dump another $60 and get them balanced somewhere else?

Should I swap one side back and determine which wheel is the problem wheel?

Any other thoughts?????