Long-time lurker, finally diving into a build of my own and figured it was time to start a thread to document the process, ask questions, and hopefully get some insight from folks who’ve been down this road before.

Car/Engine:
I’m working with an M104 engine (non-VANOS) from a W124. Planning a turbo setup aimed at ~400-500hp for a fun street/track hybrid. Not looking to go crazy, but I want it to be strong, reliable, and cleanly done.

Current Plans / Mods:
• Turbo: Still deciding between a BorgWarner S257 or GT3582
• Manifold: Custom log-style or possibly a flipped stock manifold
• ECU: Considering MaxxECU or Megasquirt
• Fuel: 1000cc injectors, Walbro 450 pump, AN lines, return-style conversion
• Exhaust: 3” downpipe, full custom exhaust with resonator and muffler
• Internals: Stock for now, with MLS head gasket + ARP head studs

What I’ve Done So Far:
• Engine pulled and on a stand
• Transmission is a 722.6 from a later model – considering the OFGear controller or a full manual valve body
• Mocked up turbo positioning and initial exhaust routing

Questions:
1. Has anyone run a 722.6 with a turbo M104? Any tips on tuning or longevity?
2. Best head gasket for boosted M104 setups? Any reliability feedback on Elring vs Victor Reinz MLS options?
3. For MaxxECU – any base maps available for M104s to help get started?
4. Oil drain solutions for the turbo – tap the upper oil pan, or is there a cleaner way?

Would love any feedback, especially from those who’ve done a similar build. I’ll keep this thread updated as the project progresses. Thanks in advance!