Hey wonder if anyone could assist we had an issue with the epc light coming on and was loosing acceleratoin and cutting iut occasionally at traffic lights etc, it gave us the code p0121 when we use our code reader. So we proceeded to change the throttle body and it's not now running even worse than before even less power the fault was intermittent to start with now it's constant, we plugged in the reader and tried to clear the code but instead we now have the code p0638. If anyone have any help or advice I'd really appreciate it. Have a lovely Sunday all ☺️

A good place to look for help with fault codes is the Ross-Tech fault codes list here and the their wiki.

Following the above I found a post in the forum saying one person found your new code came up because of a sticky butterfly valve and fixed it with a lttle WD40!

Look for the thread in the Car Repair forum for Code 001592 p0638 Throttle Body Actuator Bank 1 (J338) 

Also look at other threads for further help.