[Razeh]

I currently have a 435i at 71k miles with an upgraded CP, and I put in an order for a catless DP and FMIC. Im not really looking for HP or Torque gains and would still like to have some reliability. I originally got just the DP because I plan on opening the whole exhaust system up eventually, however I also ordered the FMIC because I am expecting that tuning the car with the downpipe with a tune like BM3 would be better for the engine than just installing it and letting it run rich with no tune.

What I'm trying to ask is should I go with stage 1 BM3 or would it be better for the engine to run these mods with no tune?

[terryd5150]

My take, simply based on your comments:

1. You're going to need/want a tune with that DP; otherwise, you'll be staring at a CEL non-stop.

2. MHD Stage 1 would probably better suit your needs; MHD tends to be less aggressive than BM3.

3. If HP/TQ numbers were your goal, I would opt for BM3 instead.

[thejeremyman9]

Originally Posted by Razeh

I currently have a 435i at 71k miles with an upgraded CP, and I put in an order for a catless DP and FMIC. Im not really looking for HP or Torque gains and would still like to have some reliability. I originally got just the DP because I plan on opening the whole exhaust system up eventually, however I also ordered the FMIC because I am expecting that tuning the car with the downpipe with a tune like BM3 would be better for the engine than just installing it and letting it run rich with no tune.

What I'm trying to ask is should I go with stage 1 BM3 or would it be better for the engine to run these mods with no tune?

First, the tune will not run rich with no tune. These are run closed-loop fueling, and things you might have heard for other platforms related to running bolt-ons with no tune do not apply here. Same thing goes for boost, OEM tune is load-based, so it adjusts boost as needed - there will be no "overboost" rich/lean, etc, with running bolt-ons on stock tune.

IC is always a good choice, same applies, fine for stock tune.

Bottom line - tune is entirely up to you. BM3 and MHD are both reliable, and it would be a little strange to leave so much power on the table and run stock tune with hardware upgrades, but nothing is wrong with it. You will get a CEL with catless DP as noted above, and both tunes can remove that for you.