engine code says po305 #5 misfire has relatively new plugs where do I need to start. engine is v6. also po174 system too lean bank 2 what would cause this?

 

Which v6 do you have?
Can you switch the #5 spark plug with a different cyl and see if the misfire moves too?
If no change switch the plug wire/or coil if COP system.
These moves may take a few minutes to do, but will help isolate the problem to the cyl or ign system.
Let us know what you find.

 

The P0174 may also be caused by the misfire on cylinder 5. The misfire allows too much air to enter the exhaust and will set the code. Do as hanky suggests and erase the codes then drive it to see if the light comes back on.

 

I had that code and the 171 code, been for awhile, and got worse.. I eventually found a vacumn leak at upper and lower air intake manifolds. if you can do the work yourself, cheap. Worth a shot for a can of brake cleaner to spray and see if any vacumn leaks. goodness knows i replaced everything else. Good luck