Can you supply a richer chip for my 4 litre AJ6 engined XJ-S or XJ40?
We could – but there isn’t any point. It is necessary to get more airflow into the engine so the first thing is to reduce the restriction of the airflow meter (MAF) and if this is correctly calibrated the ECU will still fuel the engine correctly so will not need to be modified. The only way a chip change can provide increased performance from the 4 litre is by advancing the ignition timing, which places the engine at risk of piston failure. Actually one can achieve the same effect by just moving the crankshaft trigger sensor forward a few degrees – but it is still a risky thing to do.
