Some of you will know that my gaps may have been wrong on my Sei, but I changed them today. They're now what the book says, 0.6mm instead of 0.8mm. You'll be glad to know that I even used a torque wrench :-D.
It's had a really strange, and rather big, effect on my car. It feels like a completely different engine. The gas pedal feels more responive, but the peformance seems to die at around 3000rpm (which is probably the 3,000rpm flat spot which people talk about on my car). Before the engine wanted to be revved loads, but now it seems to want to change up a gear at 3,000rpm. I also could cruise in 4th at 30mph with an 0.8mm gap, and I never felt the need to change up. Now for some reason 3rd doesn't feel right, and 4th works fine. What I find strange is that the engine would be doing exactly the same rpm with both plug gaps, but one sounds like it wants to change up a gear and the other doesn't. It's probably going to get my mpg back up to 40+
It seems like the torque has moved to a different range. I did find at first that I was labouring the engine a bit on gear changes, but got used to it after a while. I would've never expected such a big change from spark plug gaps :-o.
The torque wrench is stupid though, the scale started at 30Nm, but I wanted 28Nm. I had a good guess at it though and it's gonna be pretty close.