Since the network has a tolerance of two hours of time stamp error, does it mean one can try 14400 different time stamps per second?[/quote]
Yes. There are other limits involved but you can try more timestamps per second. The client already tries some previous timestamps if you missed them.
But if you try the next 14400 timestamps at time t, then at time t+1 you’ll try 14399 timestamps you’ve already tried, and only try 1 new. So you still try only 1 new timestamp per second.
If you do that it may still be a little easier to find a block if the difficulty changes a lot (because you’ll try more timestamps when the difficulty is low). But it’s probably not significant. And you wouldn’t get more reward, you’d only a part of it earlier.