Power increase @ 4000 miles ???

[AKlowriderZ71]

I wouldn't be surprised if they did, though. Over the years I've seen GM come up with some really dumb ideas. And I know the technology exists, when I bought new 4 wheelers, the dealer told me that the engine would "run better and have more power" after 300 miles, and he was right. He says something is programmed into the computer, has to do with break-in period.

[Lloyd-TX]

Well, according to the GM Powertrain engineer, it is nothing to do with the PCM programming.

Copied and pasted (in qoutes below) from his reply to my e-mail:

"Mr. Coulson,
There is nothing we do to restrict performance. Engines do tend to perform better as they "break-in".

Tom Read
GM Powertrain
Pontiac, Michigan"

Obviously then, this sudden increase in performance was a figment of my imagination.