I've been having the same problem. My 1998 Jeep Grand Cherokee Laredo has been giving me the exact same error p0351.
Problem is that, well, I replaced the Ignition Coil & relay as directed.
About a week later, same problem, car keeps stalling & sputtering again.
I've taken this ****jeep to at least 3 mechanics who: have put it through the same diagnostic test and have all concluded the same thing. Which is, they don't know what causing it! I can understand that due to the fact that it's an intermittent stalling so that makes it hard to diagnose. I don't have an answer cause all things are still unresolved. But, the one thing they say it might be related to is: Electrical, possibly a short in the computer/wiring harness. That's a dealer issue, well, not for me, that's too dear for my wallet.