1994 Lexus ES300 3.0 V6 252,000 miles. Automatic. This should be a simple solution. Let's look at it.

On April 1, I dropped my car off to get the valve cover gaskets replaced as they were leaking, smoking. While the garage had it, they recommended replacing all six spark plugs. Even though the car was running perfectly, I told them to go ahead with that because it had been nearly 60K miles since the last tune up. Now that I got my car back, it starts, runs, drives well; however, the car will not accelerate under a load. If I had to hit the gas pedal to get onto I-65, I would not be able to do it. Brand new spark plugs! But the car won't go. Bad spark? Fuel delivery? Somebody give me some ideas! Thank you.