I don't honestly think that "feel" will tell you if they are working or not. I think there is a natural power band in any car apart from very small naturally aspirated engines so you should feel a surge in power regardless and especially if you're trying to feel it - if you know what I mean.
I wouldn't go straight to ordering one/both though on my say so ... you need to get hold of a tester. We used to have one on the site that just got posted around. If you're happy with it as is - don't panic about it and wait to test them. I don't think there would be a fault code for it as it's not gonna impact on if the car drives or not. It won't hurt it if they are not working, indeed a guy at the RR I mentioned who owned the garage had removed the vis motors entirely but had modified the inlet maniforld so that the power/balance bits were open constantly I think and got 170ish IIRC - Stamford and Pete were there too ....
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