My old Impala still delivers. On a warm day, she did several 13.5's. MPH are down vs the past, but we think the current exhaust (Magnaflow for the 3.9 vs my old 5.3 SS setup) and the wear of the timing chain is hurting the HP on the top end. Car should be at least 1.5 MPH's more. But with 150K on the odo, nothing to complain. Still OEM motor and transmission.