[ReluctantMechanic]

I know this is a month old, but if you're like me and put it off...

I just downloaded the Haynes manual and there is a very good troubleshooting section. I have a similar problem and the troubleshooting item that seems to best match what I'm experiencing is: "Hesitation or stumble during acceleration". I notice it most when climbing a hill, but it also happens around 40mph on flat land.

The advice for this is:

1) Ignition system not operating properly.
2) Dirty or clogged fuel inector(s).
3) Low fuel pressure.
5) Fuel injection or engine control systems malfunction.

There are several others that might match your particular scenario a little bit better. I would recommend purchasing or downloading the manual and giving the troubleshooting section a quick browse. It's very comprehensive.