My TD4 has been running badly last few weeks, missing a bit at first, then losing power gradually over a journey until it struggles on hills - it eventually gives up. Just had a diagnostic check done by local indy and it shows 3 injectors have failed....is it realistic that 3 could fail like this....? 2 have been replaced in last 3 years, planning to get fixed and sell, but wonder if it might be worth getting second opinion?