Jaguar XJ (X350) 2003-2009 4.0 V8 370bhp Stage 1 Eco remap figures

Who is the Stage 1 Eco map for?

• Naturally aspirated owners who want a little more response and a more efficient, relaxed drive. Every map we list stays above standard.
• Drivers who want the small gain on offer without chasing peak output.
• Anyone who would otherwise take the full Stage 1 map but wants it tuned with economy in mind.

How Stage 1 Eco compares with Stage 1

Full Stage 1 on this Jaguar XJ is expected to give 405bhp and 561Nm (+35bhp, +36Nm). The Stage 1 Eco keeps about 74% of that power gain and 92% of the torque gain, so you get 396bhp and 558Nm: 9bhp less and 3Nm less than Stage 1, with the map shaped for efficient, relaxed driving, so it suits you if you want the pull and care about running costs. Both sit above the standard 370bhp and 525Nm.

What this means for your XJ

Without a turbocharger the improvement comes from ignition, fuelling and throttle mapping rather than boost, so expect a smaller but still noticeable change in response.

Engine management is by a Denso unit. Older engine management is simpler to work with, but age matters: worn sensors, leaks and tired components can hold back what a remap delivers, which is why we run a diagnostic check first.

We remap at our Belgrave Gate workshop in Leicester, or at your home or work within 30 miles, and every job starts with a diagnostic check.

Please note: these are expected figures, not guarantees. Real results vary with the condition of the vehicle, the ECU software version, fuel quality and the hardware fitted. Some options - including Stage 2 and anything that needs extra hardware - are for off-road or competition use only. We check every vehicle first and confirm what is achievable before any work starts.

Figures reviewed 22 October 2026.