1995 Toyota 4Runner 3VZ-E, EFI w/185K miles. Last six months have noticed slow acceleration in drive. When I take off in a Low gear I get good acceleration. A new problem recently (within the last week) has been a knocking in the engine; it completely turned off while my wife was driving it. I've flushed the engine (thinking a sticking rod), filled it with a mixture of quality oil and Lucas additive. Still no improvement. Checked the radiator and it was a little low; filled it up but still a knocking. The knocking sounds as though it's coming from the OHC. I also feel the knock in a part just above the oil pan that appears to go to the oil pump (oil sending unit?), but I can't find that part in any manual for this vehicle. I don't know what it is. Any suggestions?

Just to clarify, you say starting from drive its sluggish but if you start in first its OK.... If this is the case you have a tranny problem.

Is it a knock or a tap?
This would be a lose valve.

This sounds more like a rod knock. My Sister's '95 Runner had a knock one on start up that went away once warm, though it finally became constant, so she traded it in, rather than fixing it.

To deterimine where the knock is comming from pick up a stethoscope, and listen to the engine.

Could be a broken plastic Reed Valve cover. I have the same and I need to purchase the whole unit. The knocking sound is only on at certain rpm . . .