hi, im looking or advice ,i have a 2012 4.4tdv8 on ocassion when driving in traffic at low speed it jerks and howls, also if taking off hard it can howl and twice i have lost all power until i lift off accelerator. last week pulling a trailer 2 tonne it howled for about 5 seconds when taking off uphill.works perfect 99 percent of the time . gearchange is very good with no delay . any advice would be appreciated . thank you . sean

Could the secondary turbo inlet isolation valve be sticking?