Fueling In M4.3 and M4.4
M4.x turbo Volvos use a return-type fuel system with a rising rate FPR that maintains constant injector pressure differential by referencing manifold pressure. The pump runs at 100% duty, making oversized pumps problematic. Factory injectors, FPRs, and fuel trims are covered, with practical recommendations for turbo upgrades, E85, and NA-to-turbo conversions.