Yeah, it's clear that the dyno was miscalibrated or something. I had one of the highest dynoed NA 3800s and I put down 222whp:http://m.youtube.com/watch?v=GUiTG0YT4i8

Most stock 3800s put down 150-160whp.

 

As others have mentioned, that number is impossible on a stock engine. Assuming your engine is in 100% shape, you can take your factory crank hp # (200), you can subtract about 20% to figure out what it should make at the wheels to account for drive train loss (with the wheels/tires on, a hub dyno will read a bit higher). Your k&n might add one or two hp, but that would be in the noise of the dyno from one pull to another. It could be even lower than that though depending on the engine's mileage and condition as that's a best case scenario.

Just to give you an idea, 235 whp on an NA 3800 would take heads and a cam at least, heck the stock supercharged 3800s are barely hitting 200.

Some things to ask your friend to see what went wrong:
-See if it is a raw number, or an adjusted number. Some dynos can add a correction factor for temp, humidity, etc and it's possible that they just fat fingered one of the data points so that it artificially skews the data too high.
-You could also see if he was doing a conversion to calculate crank hp. Some shops do this for people who aren't familiar with whp numbers but are used to seeing the crank numbers advertised by manufacturers so they can do an apples to apples comparison. Perhaps they just miscalculated the conversion?

It would be nice if you could get some usable data out of it so you weren't beating on the car for nothing.