i call them a she because sometimes they can be a b tch to fix and real expensive to maintain.

 

So I had a similar problem. Went through everything on the motor (I had three) so I replaced everything. Nothing fixed it so I then assumed it to be a wiring harness. Before I changed that I checked the fuel pressure and it was low. Changed the fuel pump and a problem I had for a year was fixed. It didn't make a whole lot of sense because just like you washing the motor and hitting mud holes made my truck run very odd until it dried. I also picked every mechanics brain I knew. TPS and AFM were the two things brought up a lot. I actually ran it without the TPS plugged in cuz it would run better. I would check your fuel pressure. However, 6 months later I had another similar problem arrive. I thought great fuel pump went again until my battery died and I figured out my alternator went. Yours sounds more like a fuel issue though. Like I said check the fuel pressure.