My BBK TB on my 95 was fine. Buddie's BBK TB on his 04 was garbage. They are VERY hit or miss. First thing you need to do is put the stock TB back on to rule that out. My money is on the TB being the culprit.
If it is the TB return it and get a Dragon or Accufab.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.