It been happening for a couple months and has been getting worse. The first start up and drive I’d be on the highway cruising in 5th gear and my rpms would drop from 3k to 1k almost stalling and my service engine soon light would come on then go away and the rpm would shoot right back up to 3k. It’ll do this once or twice during The first 10min of the drive then stop. I am full bolt on have a Cobb access port and waiting to get dyno tuned. I baby the car rarely go into boost. Changed the spark plugs and fuel pump still have the problem any ideas? It’ll have its days where it won’t do it.

 

There is a very common vacuum line leak that does exactly what you're describing. Check to make sure it hasn't popped off, and (regardless of if it has or not) ziptie that sucker in place.