I have a 2006 Escalade with 230K miles. I love the thing and after seeing what it would cost to get a newer one, I have decided to throw about $3K at mine and run it for another 2-3 years. I've never had a vehicle go 300,000 miles, and maybe this will be the first. Anyway, it has the 'check suspension' alert (and has had for about 80K miles). The rear suspension still rides fine, but inspection has shown that the bellows on the rear shocks are likely leaking a bit, which is probably the reason for the alert. I have the Z55 autoride suspension. A GM replacement rear shock is $325 from Rockauto. They also list an SKP for $140. I'm not familiar with SKP - has anyone used this shock?