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?