LR 3lt Secondary turbo bypass valve vacuum solenoid test

LR4/RRS 3 lt twin turbo 180 Kw/600 Nm intermittent fault "Restricted Performance" and increased fuel consumption. Thought I would check out the operation of the vacuum solenoid on the secondary turbo bypass value as I was told it might be sticking. Still got the issue and this solenoid seems to be working fine. Was told the solenoid works with PWM but I can not see any evidence as multi meter needle movement was steady and no blinking of the LED, vacuum was also steady.