P0401 - Exhaust Gas Recirculation Flow Insufficient

2002 Galant I4 with 102K miles. I've been trying to get this code to disappear for a while now to no avail. I've read info on this forum and replaced both the EGR solenoid and the EGR valve. Cleared the code but it comes back after driving for about 15 miles. The car is running perfect, no hesitation or rough idling.

Prior to replacing the solenoid and the valve, I noticed the tube that was connecting from the EGR valve to the EGR solenoid was disconnected. After re-connecting the tube, the car immediately started idling really rough and would die if it went below 1K RPM's. I then ordered a new solenoid and valve from Amazon and replaced both (including the EGR valve gasket) and also cleaned both intake manifold ports that had some carbon build up.

Like I said, the car is running perfect, except for the damn code that keeps popping up. I checked all the hoses and they are not blocked, no cracks or anything. I read that TB gasket might be an issue, so I'll be removing the TB today and check the gasket but honestly it's never been removed, at least by me. When the car reached 100K miles, I had my mechanic do the timing belt, so I don't know if he had to disconnect the TB for that job or not, if he did, it's possible the gasket was put back on wrong...

Other than that I don't know what else to check. Any help is much appreciated!

Edit: TB gasket was in correct position, I cleaned it and the TB while it was disconnected and put everything back together.