Krank, there are a number of things to look for here. I had numerous little troubles with my P2 install.
First, I would take the engine out. I know, it's a hassle, but I would definitely do it. Take off the EZ-start and make sure that one-way bearing isn't grinding away at the backplate. Make sure the back plate is tight (4 screws). Now, remove the HSN from the carb, (counting turns so you can replce it at same setting). Also remove the HSN seat assembly. Now spray all those parts (including the carb) with something like WD-40 and blow them off with compressed air, keeping things as clean as possible. I would also take out the fuel tank and give it the same treatment, blowing out the tank and lines. Re-assemble the engine.
Now, re-install the engine, and with air cleaner off, work the throttle linkage (engine off) using the TX. MAKE SURE there is nothing hitting anywhere. I had clearance issues with the ball cup hitting the spur gear nut at WOT. It took me about 15 minutes of careful re-positioning just to eliminate this one problem. I also had issues with the linkage not letting the idle return all the way back to the set screw. At idle, you want to make sure that the idle set screw is actually controlling the idle. You don't want the throttle trim adjustment controlling the idle. Make sure you have a little room for take-up before the linkage actually starts pulling the carb open. Also make sure you have enough spring tension to pull the linkage back. I added a throttle return spring.
Also, make sure the carb cinch-pin assembly is tight. Mine actually vibrated out and I had to get a new one.
After you re-install engine, check and re-check the linkage, I would start the truck and run it on bench with air cleaner off. Blip the throttle lightly and (by looking into carb bore) make sure the carb slide is returning to rest against the idle set screw. Your servo may be glitching enough to prevent it from returning.
Once you are confident that linkage and servo are good to go, then I would look at fuel adjustment. High idle almost always mean too lean somewhere. I would richen up LSN. It might take a lot. Richen it up til you get good stream of smoke out pipe. Run around at half-throttle or less and see if idle seems OK. If idle and part-throttle performance is good, then I would try some higher speed runs. If high-speed idle problem returns, I would start richening up the HSN til it goes away. Of course, then you need to re-set LSN. Some guys will say always set HSN first, but it don't matter so long as you finish up with LSN. HSN affects overall fuel flow. LSN affects off-idle to about 3/4 throttle.
Lemme know how it works out.
