Engine stumbles or dies on acceleration from stop

I have a 1985 Toyota Camry Le, approx. 73,000 miles, automatic, 4 cyl. About a month ago, every so often the engine would be hard to start in the mornings. I took it to a mechanic and they said the fuel pressure was low. I put in a fuel additive to clean out the gas tank, and I haven't had this starting problem since. However, a new problem developed shortly after this. After I warm my car up in the morning, back out of the driveway, change from reverse to drive and then accelerate, the engine will stumble, and sometimes die. When I restart, the engine sometimes stumbles again, then it works fine. Other times, when I'm at a stoplight, I will have the same problem - when I go to accelerate, the engine will stumble, then die, and I have to restart. I've also noticed I have a low, rough/uneven idle. I also hear a clacking sound when I accelerate at freeway speeds or uphill. A couple weeks ago, I had a Toyota specialist do an ignition/fuel injection system diagnostic, and they said my fuel pressure was good, but I may have a bad pickup coil/igniter/ignition coil. I've replaced the alternator, drive belt, spark plugs, and air filter. I'd appreciate any light you could shed on this problem. Thanks.