As the title states my car is only boosting 10 psi WOT. Here are the facts:

• Issue is intermittent. Happened 3 times in a 2 week span
• Scan with OBDII get P0420 code ( from after market exhaust) and code for a bad thermostat ( procrastinating on changing) . I have gotten a code for low boost once.
• When codes are cleared the car functions fine with the stock 15-17 psi of boost.

the first time it happened I thought it might be the lower charge pipe I just installed a few weeks ago. I checked the clamps for leaks and all is well. Any Ideas?