Random engine misfire - 99 spyder
 

Hi guys,
I have a 99 eclipse spyder and for the past year and odd, the engine seems to stumble at random (and the rpm shoots sky high). When I ease off the gas pedal and slowly work it back, the stumbling usually goes away after a few attempts. However, sometimes the stumbling becomes worse and the check engine light comes on - strangely, the car seems to come back to normal after the check engine light comes on! I have taken it to quite a few mechanics but they were not able to identify any underlying issues except the random engine misfire code. Recently, I took it a new mechanic who mentioned that he had seen this problem with quite a few Mitsubishis and thought there was a TSB out on it. Any ideas what's causing this?

Thanks