I have replied to your dilemma previously, but if you are still having lack of power, and erratic rpms , I think you damaged the throttle body and/or the MAF. If there are wires going to the throttle body, they have sensors or some kind of a mechanism that is internal to the throttle body. These report to the main computer and make the C5 perform, or not perform correctly. Obviously it is damaged internally . Don't feel too badly about causing the issue by cleaning the throttle body or MAF because it or they must have been faulty before you did the cleaning. The cleaning unfortunately made is worse. If you wind up having to spend the the money on a new throttle body, you might as well get a remanufactured GM or just get a larger one from any high-performance shop. A larger throttle body does make a big difference.
The MAF has many issues that can go bad. Any capacitor could be bad or the circuit board could be cracked. A hairline crack could cause it. I had this issue with a Saab 900 turbo and the problem was the throttle body. I paid 1500.00 to have the problem diagnosed and a new part installed.
If your car has aftermarket exhaust, the oxygen sensor may need to be changed to a Y band oxygen sensor than a narrow band one. A Y band oxygen sensor requires an external gauge set up in the cockpit of your car. It is possible the oxygen sensor is the whole issue. It is a lot less expensive to replace than the MAF or the throttle body, it may be worth a shot. I wouldn't think the issue is that you need a Y band sensor, a couple of stock new ones should do the trick...