Had to remind myself, so just went out and looked at my carpets.

On the passenger side, the pad was still good, so I re-used it.

On the driver's side the pad had disintegrated. I made a new pad out of two layers of 5/16" black Eco foam carpet underlay that I bought at Home Depot (Canada). It worked well.

I don't recall having any problem getting passenger side pad off. But I have forgotten how I did it! Perhaps if you can peel up one edge and get some solvent (adhesive remover, Varsol or??) started in between the pads and the carpet, you may be able to pry the pad?

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5