Thank's Mike for your kind answer.
I think I will give the whole story of my problems with the Throttle body. It is unfortunately a long and not funny story. But I hope it will be a happy ending, sooner or later.
After installing the Magnuson TRV 2300 I had 2 - 3 lovely months without any problems. Then some awful lights began to light up in the instrument cluster. Check Engine light and MIL light. TCD's were P2135 (Throttle position sensor 1-2 correlation) and P1516 (Throttle actuator control position) and P2101 (Throttle actuator position performance). When the TCD's where erased,the awful lights were turned off, and engine went well again. After a couple of weeks, however, the lights came back, and they have been done that occasionally. Sometimes they have dissapeared of their own, sometimes i have erased the TCD's. After consulting Mike, I obtained a throttle body from GTO ( 12 570 790). However, it was not new, but used.
However, the problems with the lamps continued in the same way. In addition to that, the idle speed was very high (1400 rpm) and then the gas was hanging when I released the accelerator pedal.
Recently I have tried a third TB bought from a Chevy dealer here in Sweden. (number is RME87)That gave new problems. The engine had very bad bidle, it was close to stalling, and quite bad at all other rpm's.
I have now tried to get help from the company that did the tuning after the TRV 2300 installation, but they have been unable to help. They have advised me to get a new throttle body, exactly the same as the original.
And that is where I am now. I do not know if it's the right way to go, but I have to try something. I hope the 126 79 524 will help and give a happy ending to this.
//Lennart