Here's the foolproof tuning method for the perry pump, if you try to tune with the adjustment screw on the pump, you will lose all your hair, and throw the pump onto the ground and stomp it to death, save yourself the heartache.

Open up the muffler if you've had it blocked off, peak the high end, don't back off rich. Go to idle, if engine idles well for 15 or 20 seconds, lean the low speed 1/4 turn, Go back to the top and re-peak, go back to idle, same routine, if it idles for 15-20 seconds, lean another 1/4 turn, continue this process until engine will not sustain a idle, it should speed up and die within 20 seconds. Now richen the low speed 1/16th turn at a time until engine will again sustain a idle,after each adjustment on the low speed repeak the top end, as soon as the engine will sustain a idle leave the low speed alone. Each flying day just repeak the top end and back off 150 rpm for flying.
You have to go lean to the point of no idle then come back up to get it right. Transition from idle to midrange up to full should be crisp without sputtering. If you run the high speed to rich you will have the same problem with sputtering. My O.S. 160 preforms flawlessly with this setup, I had to lean the low speed 1-1/4 turns to get it to run properly, just make sure you peak the high end and only back off 150 rpm, be sure to use a tach. On my 1.08 it took about 7/8 of a turn on the low speed to get it right.