I was in rush hour yesterday and I was in third gear going about 25 mph. I noticed that if I gave my 98 EX 5-speed just a bit of gas, it would hesitate (if you rock back and fourth in your chair, that's what it was like). If you gave it WOT, it wouldn't happen, and it doesn't happen in any other gears. I just replaced the plugs with NGK-Rs about a month ago.

Any ideas?