Airtec Motorsport BMW S55 Hot Side Boost Pipes M3/M4/M2 CompAirtec Motorsport BMW S55 Hot Side Boost Pipes are a direct replacement for the plastic OEM boost pipes, which are more restrictive and prone to cracking especially with increased boost pressures from tuning. The pipes have been designed to improve the overall internal diameter and flow of the original OEM pipes, which flatten considerably where they pass over the top of the engine. The Airtec Motorsport replacement pipes are constructed from alloy,