The Cobra was a beast when I had it but I wouldnt really say it was easy to tune. I didnt have any trouble but a bunch of other guys who had them did. I think it might have been just they were too scared to lean it out enough. I used 1.0 springs and carbon shoes and never ever had trouble clearing any size jump no matter what kind of run up there was. Its a really strong engine through the entire powerband. If you feel you need 1.1mm springs to get enough bottom end my guess is your too fat on bottom. I also found that to get the best results from it I needed to tweak the midrange adjustment slighlty. BTW I used a JP-3 and 30% fuel without the extra included shim for plug I am pretty sure I used an Odonnell 77.