How much can a 2.0-liter four-pot withstand and still be reliable? For Mercedes-AMG’s new-gen A45 S, the magic number is 421 PS (415 hp / 310 kW) and 500 Nm (369 lb-ft) of torque. For B&B AutomobileTechnik and their Volkswagen Golf GTI TCR, that number is a little bit higher.

With the Stage 4 power upgrade up and running, this front-wheel drive hot hatch enjoys a whopping 450 PS (444 hp / 331 kW) and 580 Nm (428 lb-ft) of torque.

The additional 160 PS (158 hp / 118 kW) and 210 Nm (155 lb-ft) have dropped the 0-100 km/h (0-62 mph) time from 5.6 to 4.5 seconds. With the speed limiter removed, the car can max out at over 280 km/h (174 mph).

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Opting for the tuner’s Stage 4 kit will blow a €12,950 ($14,295) hole in your bank account. The bundle of upgrades includes the addition of a larger turbocharger, high-performance intercooler, racing exhaust system with sports catalyst and a new engine software. The 7-speed DSG has also been reinforced.

Stages 3 and 2 cost €7,950 ($8,776) and €3,950 ($4,360), respectively, and offer 400 PS (394 hp / 294 kW) and 520 Nm (384 lb-ft) of torque, and 360 PS (355 hp / 265 kW) and 470 Nm (347 lb-ft). Stage 1 lifts the output of the four-banger to 340 PS (335 hp / 250 kW) and 450 Nm (332 lb-ft) and is available at €1,498 ($1,654).

You could also spend extra and get the €298 ($329) lowering springs or invest €1,798 ($1,985) in the coilover suspension. For €3,795 ($4,189), the high performance brakes become available, with larger front discs, whereas the exhaust system with catalytic converter that offers a deeper tone is a €2,795 ($3,085) option. Meanwhile, B&B’s 8.5×20-inch wheels, shod in 235/30-20 tires, have a €3,298 ($3,641) price tag.