[V8] driveability 2

[John Dodd]

Here is more info on my previous problem:
     1. Started the car  after sitting for 2 days. Idled OK at 1000
rpm.When it got warm it started to miss again.
 Rpm fluctuates by about 200-400 rpm always lower (800-200 rpm.)
 The car runs Ok for 10 -20 seconds at a time then starts again with the
idle issue ,then runs normal and so on.
Drove around the block ,feels less power. Reved the engine, while in
park at 4000 rpm but with difficulty.
 
2 .Read the ECU codes again. Came up with 2413 .Is it possible that I
have a vacuum leak ?
3. My O2 sensor and FPR were changed 20000 km ago so I assume they are
OK.
 
Any pointers on where vacuum lines are located so I can check them ?
Also how do I check for a bad injector ?
 
thanks