I just did my 3.4 swap and after I got most of the early problems worked out it ran fine for a couple hundred miles but now when its cold it starts hard, won't idle. Sometimes I have to start it 4 or 5 times and you have to keep your foot on the gas. After a couple of minutes it idles on its own but the RPM jumps back and forth between 500 and 1500. Once it get warm it runs fine but the idle stays way to high, like 1500 RPM. Is this a choke issue or do I still have a problem with the 4.3 TBI ajustment. I never had to do anything other than get the vacuum lines correct. The TPS from the old 2.8 TBI bolted right onto the 4.3 TBI. The injectors and the TBI were completely rebuilt.