The N52 / N51 FAQ.

For both N51 and N52, the Stage 1, Stage 2, and supercharger tunes have been consolidated into a single product page — pick your stage there.

Stock car / airbox / rear exhaust only

Start with the tune — it's the single biggest gain per dollar.

Full bolt-ons

• 3-stage intake manifold or N54 intake manifold
• 22RPD tune
• Weight reduction
• 3.73 or 3.91 rear differential (front and rear 3.91 if AWD)
• Straight-through muffler
• XHP Stage 3 transmission flash for ZF6 auto (only 06 325/330 & 528i)

You do not need to upgrade your injectors or fuel pump unless you're running E85 or boost.

• E85 — requires larger injectors plus the 22RPD Stage 2 tune
• Boost — requires the injectors, and possibly a fuel pump past 400+ whp

It's not plug-and-play — but it's straightforward. There are two routes.

OEM+ method

Follow the full guide below (thanks to Alphonse / Biginboca for the writeup).

Easy method

• Eccentric inserts
• Catch can to delete the CCV — the included hoses won't work, buy fuel-rated hose and cut to fit
• Buy a used N54im throttle body to attach the fuel evap hose to (it has a port for it)
• 2006 models require soldering an 07+ throttle body connector to run an N54 throttle body

If you have the DISA valve shown below, you have the 3-stage intake manifold. There's a second DISA on the lower inner portion under the runners.

If you don't rev past 4500 rpm, the 3si makes more power in that range. If you spend more time above 4500 — especially manual or ZF6 auto with XHP and a raised redline — go N54im.

• With a 7500 redline, at WOT you're always in the N54im's peak powerband, which outperforms the 3si
• N54im has no DISA failure points (which can kill an engine)
• N54im has a more linear powerband
• 3si has more low-end torque

Main benefits of the N54im

• No DISAs — save ~$800 and remove the risk of engine damage from failure
• Extended powerband — 3si drops off at 6800, N54im pulls to 7500

Going single-stage → N54im ($80–100 used + $400 tune) vs $800 on DISAs + $80–250 for a 3sim + $400 tune for nearly the same torque — the N54im gives a broader powerband and more peak HP, so it often makes sense. If your car came with the 3sim and rarely sees above 5000 rpm, there's little benefit unless you just want to avoid replacing DISAs.

They don't exist. Buy genuine BMW DISA — the OEM manufacturer (Mahle) doesn't sell them un-branded by BMW. If a DISA valve fails, it can cause engine failure.

Two popular breathing upgrades beyond the manifold:

• D-style ram air intake — feeds cold air to the airbox
• MILVS (Modified Intake Lift Valvetronic Supports) — increases intake valve lift

Listings frequently go out of stock. If the link expires, search "328i headers" or "N52 headers" and match the product photo. Order the ones with the O2 sensor bungs located after the merge, and use OEM gaskets.

Always specify to the seller that you need the USA version, not the EURO version — regardless of the car's origin. The Euro version has fitment issues, an incorrect head flange, and incorrect oxygen-sensor placement. Use the photos below to confirm which you're being shown.

We've seen lots of positive reviews for Gravity Performance Headers. We are not affiliated with this company.

Without headers

• Muffler delete
• 135i N54 muffler + resonator delete

With headers

• 3" exhaust merged at the transmission mount
• AA Gen 2 muffler

• Broken CCV hose
• Ignition coils
• Spark plugs
• Vacuum leak
• Leaking valve cover gasket

A smoke test pressurizes the intake to find vacuum leaks — a common cause of rough idle and misfires. Here's the procedure.

The WOTBOX enables flat-foot shifting and launch control. Full wiring and install steps are in the guide below.

A simple extra step that makes a valve cover job much easier.

After a battery disconnect, valve cover job, or Valvetronic motor service, the system needs to re-adapt. Here's the quick procedure.