Test drive a different one this time. Not all cars are equal. In a lower class of quality control my preferred rental car was the mustang until the 2005 model came out. I've rented over 50 of them on business trips and I've seen that each with low mileage of under 5K miles could be really nice or really bad. Brakes, suspension, shifting and power all quite different. I'd say a difference of 30-40HP between the worse and the best. Some would always shift like a taurus some I could get to snag 2nd everytime. I've had similar experiences on test driving other cars so drive 2-3 and even pick a 335 to see if it feels the same as the 135i as it should feel close enough.
2008 135i - Cobb/JB4, Spec 3+ Clutch/Flywheel, MS DP's, Berk street exhaust, AMS IC, UI CAI, CDV delete, Quaife LSD, M3 control arms/Links, RE Toe Link, ECS Trailing Arm, M3 rear SF & Trans bushings, SS brake lines, Michelin PSS.