Let me introduce my favorite sleeper build.
And what's under the hood:
That's "B254T", 2.5l turbocharged 16v 4-banger, built to produce about ~500bhp+ on track and "mere 139bhp" on street.
-Motor: B254T on street 139hv/217nm and on track 496hv/595nm
-clutch: SRE 618+ dual sprung plates
-transmission: BMW 265 Getrag
-prop shaft: BMW / Volvo 940 / Toyota Hilux hybrid
-rear differential: Toyota Hilux, original LSD, 3,9:1 ratio
-BC-racing adjustable coilover suspension kit
-Steering: BMW 320 powersteering rack
-Gauges: Autometer. RPM, speed, fuel, coolant, boost, oil pressure and clock. PLX-wideband lambda
-ECU: DTA P8 Pro
-Cooler: Chinese 550*300*76, slightly modified
-fuel system: 2x "bosch 044" pumps, 1600cc injectors
-Front Brakes: Discs Mazda 6 275mm, brake calipers Wilwood Superlite
-Rear Brakes: Discs Mazda 626 261mm, brake calipers Volvo V50
-Brake booster: Volvo 850 tdi
-turbocharger: Turbonetics GT-K 650
-Intake manifold: Volvo 16v/Sierra Cosworth/Apupoika hybrid
-Exhaust manifold: 4-2, 48mm tubes. Primary length 65cm
And from
HERE you can find all build related images, like the sheer amount of parts he has done himself, just because he can.