I recently picked up a 2004 Neon SRT4 and it was having an overboost issue. We removed the battery and the turbo intake pipe, and were finally able to see what lines went were. We followed the diagram on the hood and found that the line from the TIP Solenoid (Solenoid #1) was going into the waste gate. The line that was supposed to go to the waste gate (#2 Solenoid, black line) was going to a T line that appears to go to the charge pipe in front of the throttle body. The other part of the T line, I have no idea where it goes. I've attached a picture showing the T line.
We swapped the two lines (black to waste gate and the red going into this T line) and my overboost issue was resolved. It holds steady at 14psi through 2nd and 3rd gear pulls. Before it was going as far as possible (beyond 20) and blowing the vacuum line that runs the power brakes.
Now overboost is resolved, but she doesn't idle down after any throttle input. She holds idle at around 2500-3000 RPM for five-ten seconds and then idles down to 800-1000 RPM. I don't know if this is a totally separate issue or the red line from the Tip sensor is just plugged into the wrong spot.