IMO, it may depend on what gear you are in at the time you hit the gas pedal, and the speed that you are traveling. When I first got my Z 6 months ago, I noticed a similar situation, but found out that if you drop a gear or two and bring up the r's, no problem. I thought that at any gear with the LT5 it would be instant, and again depends on your speed and what gear you are in.
I don't think that one plug even if running rich would cause that situation, IMO, it would have to be loaded and fouled out for you to feel anything.
Just had ours out today, always a great ride.....have fun.....
