I have a DA 100 which has 3 gallons of Lawnboy and 2 gallons of Pennzoil 32-1 run thru it. About six months went by without running it. Today when I ran it, the top end is good but the idle was rough and would not reduce down like it used to without quitting. I had to richen it to get it lowered but then it loaded up and sputtered in transition to high end. I'm sure the carb needs cleaning. Besides the screen needing cleaning, is there a low end carb jet that I need to clean? Your help would be appreciated.

You need to run it more and get the cob webs and trash flushed on through it. The diaphragms probably dried out while it was setting?

If you have run 3 gallons of lawn boy, ILL bet your rings are stuck up.

The Lawnbow probably generated a lot of soft carbon, some of which is likely built up around the plugs. The Pennzoil is cleaning that crud out. Takes some time. Since you mentioned not knowing of a low needle it suggests the engine has yet to be tuned.

The carb has two needles. The one closest to the engine is the low end needle. Usually both needles have an identifier cast into the carb body next to them . One an "L" and the other a "H". Rather than write it all again I'll suggest you run a search for gas engine tuning threads. There are quite a few of them and many have the right information. There may be a gas engine for newbies "sticky" at the beginning of this forum.

Patience and a little work and everything will work out just fine.

When an engine is stored with gas in the tank and carburetor, the gas evaporates and the oil remains.

That oil attracks dust and when fresh gas hits the tank, it gets diluted and adds to the oil content of the new fuel.
The oil deposits in the carburetor clog filters and disturb valves.

Spark plugs and carburetor are not happy with that extra dirt and oil.

That may be part of your problem.

Best luck with that!