Hi,

I have a 2017 Series 5 Auto Barbarian, I have owned it for three years and became aware of the EGR delete wire. I drive like miss daisy, but unlike others I struggle to get 30mpg. I bought the lead mainly for the potential increase in fuel economy. I fitted the adaptor lead to the mass airflow sensor and immediately noticed an increase in MPG, averaging around 38-42MPG, a massive increase. I understand the wire contains a resistor that effectively fools to ECU into thinking it is -18 degrees (or similar). This in turn, keeps the EGR valve closed.
I noticed that the engine sounded louder and a distinctive engine rattle, sounding like "pinking". This occurred generally upon light acceleration around 1700-2000RPM. It occurs at all times, mild /freezing temperatures, engine cold /hot. As it started shortly after I fitted the lead I decided to removed it. The pinking noise stopped, I refitted it again and removed to confirm it was definitely the cause. I have now left it off. The seller suggests that the MAF input to the ECU is for the EGR valve only and has no bearing on fueling etc, no adverse effects on the running of the engine etc.
Clearly something has changed when the lead is fitted, my question is; does the MAF input just control the EGR valve, or is that a fib to get you to buy a lead, or is the rattle just caused by the slight increase in combustion temperature caused by the EGR being permanently shut. If it is, what can be done (if anything) to counteract it. I have read online that fuel octane additive would help, as I have bought the lead to increase fuel economy it does seem pointless if I then either have to buy super diesel or use fuel additive. Any thoughts? Thanks in advance!