Engine? Driveline? ... Bumper?
 

I'll just go with details first.
65-70mph, 6th gear, passing, into boost a bit.
For about 1 full second maybe a bit more, power drops, but isn't cut out. I hear what can be best described as taking a 3 inch round steel bar and rapidly beating the side of a commercial trash can. but not insanely fast. No metal sounds, just that deepish thuding. sounded like it was from the right half of the car, maybe even out towards the wheel well but with power involved.... meh.

Did this 3 times in about 30 seconds each only for a second as I got outta the gas as best I could. After that another 40 miles, i slowed a few times, gave it some boost in 6th at 55 through to 75, and 5th 50-75. Never happened again. No ongoing sounds, no ongoing shakes, rattles, or pistons and rods playing peakaboo. I have no idea.

Do you?

So many issue with this car that are small, and either due to the mods or cosmetics, this now has be KBB'ing the value.

knock?

Possibly described that way in the event, but I don't know what knock sounds like to be honest. I imagine a higher pitch of sound, this was low. But then no def not afterwards. Thing sound fine right now.

You're hampster wants off his wheel. Or wants you to feed his meth addiction.

Not much action here eh? Guess these threads get old after 4 years.

gave it boost in 6th only going 55??!! That sounds like a recipe for disaster. Downshift dude!! Our little turbo produces too much torque down there. There are many a boom tale while under moderate acceleration in low rpms.

the brownie's got it right.
downshift