Does anyone have a source of good information on the engine specifications on the Apollo? I know it uses a biturbo Audi 4.2 V8. That's about it... I'd love to know more about which engine block it uses, which heads/valvetrain, what type of fuel system, ignition system, turbochargers, etc. if for nothing else than to imagine how to build an 800bhp RS6.

So far, this is the most information I could glean, thanks to Wikipedia:

The Apollo uses a 4163 cc bi-turbo intercooled version of the Audi V8 engine.[8] The 90° V8 has a closed-deck light metal crankcase with dry sump lubrication. The light metal cylinder heads have five valves per cylinder, four overhead camshafts, VarioCam Direct variable valve timing on the intakes, and hydraulic valve clearance compensation. The double-flow exhaust system has four oxygen sensors to monitor the gas mixture, and a 3-way catalytic converter. Modern controls include an on-board diagnostic system, eight-coil electronic ignition, sequential multipoint fuel injection, and an electronic (drive by wire) accelerator system.
There are 3 engine types available:
Base version - approximately 650 PS (478 kW; 641 bhp)
Sport version - approximately 700 PS (515 kW; 690 bhp)
Race version - approximately 800 PS (588 kW; 789 bhp)