I may have this issue. Car was idling funny a few days after I purchased it at 98k miles. There were these pops and puffs from the exhaust and tough idle. I never over revved it, I was told an old man owned it before me. And he kept the car in immaculate condition.

I changed the plugs and tried 2 different sets of coil packs. Today a valve adjustment was performed by a s2000 specialist. Still the problem persists.

Losing hope.....

 

Arise dead post! Arise! lol.

What about injectors? Have you had them cleaned? Several years ago I chased around all the same symptoms and it ended up being injectors...