30th6

iTrader: (6)

I have a 09 g8 gt with 181k miles, it started idling high and throwing a po 507 code. I took the throttle body off the car and cleaned it with throttle body cleaner, and I cleaned the mass air with mass air cleaner. After I put it all back together it runs with a higher idle now. I've unhooked the positive cable on the battery for a few min then attempted the relearn process. Idle for 3 min, shut off for 1 min, idle for 3 min with no luck. I've swapped the throttle body with another supposedly good ls2 throttle body with no change. I've pulled the throttle body off my 08 5.3 and put it on the car and it runs perfect and does not throw a code. I've even switched the mass air off the 5.3 also with no change. The motor idles at 1200-1500 rpm with the stock ls2 throttle body. Any ideas before I buy a brand new $500 throttle body and hope it fixes it? Why would the 5.3 tb run better than either of the ls2 tb unless both are bad?
there is no vacuum leaks that I can find.