[Elderado82]

What should I expect in terms of HP with a JB4, an intake, a catless downpipe, and an E30 or E40 mix? I understand the website mentions a 75 HP increase, but that's without the catless downpipe and only with an intake. What other supporting modifications should I consider, whether for additional power or peace of mind? I'm planning to replace the spark plugs at 50,000 miles and install the JB4 along with the aforementioned mods and a chargepipe. The car in question is a 2021 M340i xDrive. Additionally, I'm not currently considering an ECU flash, as it would require sending it to FEMTO.

[mike@x-ph.com]

The Jb4 does not max out; you can add as much boost as you want until the engine breaks.

Your HP will depend on your map; as a general rule, 1 PSI is ~ 15 whp and ~20 wtq.