My VDP, affectionately called "J2" has not been running great for some time; like many months and it would occasionally throw the P0174 code. I have done a great deal of work trying to correct what I figured was a vacuum leak; replaced the manifold gaskets, spark pugs, injectors, various vacuum hoses, throttle body gaskets, etc. but still the problem prevailed, albeit on an intermittent basis and the occasional P0174. (When checking the fuel trims, the numbers were very similar to my other VDP (J3), which never throws a code.) Sometimes it would run fine, sometimes it was sort of misfiring slightly; running unevenly. Finally about a month ago got the CE light and code P0358: coil #8 failure. After replacing that coil, the car has run perfectly. I think the coil was weak for a long time and finally failed entirely. I have waited to post this message for some time to see if the car was actually repaired but all's well now.
It would be great if my ODB testers could show a slight misfire on any particular cylinder. It would have saved me a lot of time!

 

Thanks for letting us know. I will make a note of that in my X308 folder, in case I should ever come across this obstacle...