Hot Rodding a 2005 Cadillac STS V8

I am at wits end!  I want to hop up my 2005 Cadillac STS beyond the exhaust, Cold air, and spark plugs.  

 Nobody makes a programmer for it, but they make one for the 2006+ STS-V and the 2007+ STS V8/V6 models.  My questions are:

* Does anybody know of someone/company that can custom program my ECM?

* Can the computer and wiring harness be changed to the 2007+ harness & ECM (understandably there may be some sensor changes as well)?

* Can the harness & ECM from the CTS-V be used in the STS with an LS motor I am building?

Any body that can provide insight or point me in the right direction would be greatly appreciated.