Tires ..... When you say twitchy, does that mean they handle squirrely?..... and when you say grooves, do you mean the natural ruts in the road, or the longitudinal texture cut into the road?

Brakes ..... Many manufacturers make a product generically called "anti-squeal paste". At every brake change this product should be applied to the backside of each brake pad to prevent the very noise you describe. Either the garage omitted that step, or the paste they put on isn't very effective. This noise does NOT mean you have poor pads; it's just an annoyance.

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95 E320 Cabriolet, 159K