I just checked the 4runner forum and noticed some similar entries, but here's my problem:

As I was accelerating up an on-ramp my 4runner acted as if it was running out of gas, I let off and then applied gas and it knocked and sputtered.
I pulled to the side and let it idle in park (gas gauge reading 1/2). I applied gas while in park and it would knock and sputter at 2k rpm.
I shut it off and let it sit for 5 minutes. I turned it over and after idling for a minute I was able to apply gas and bring the revs up smoothly.
I pulled on to the highway and was able to drive normally at 65mph/ 2-3k rpm. About 1/2 hour later(I was an hour away from home) I went through the same thing...loss of acceleration-power, knocking, pulled off...shut it off...restarted and drove home (40 miles) without incident and normal power delivery.
I'm going to go over everything in the am, but this is the first problem I've had with it. Bought it in 2003...it now has 118k miles on it...no problems at all- so I've been lazy about getting under the hood. Trying to avoid going to the dealer until absolutely necessary.
Thanks in advance for any help.