I bought a GX 160 from an old pressure washer and replaced the crankshaft because it had 6:1 gear reduction and gave it 22lb valve springs and removed the internal governor, I bought a re-jet kit from eBay that came with a pilot jet emulsion tube and .37 jet .36 jet and .35 jet. I tried all of them with the E-tube that the kit came with and it seemed rather 'boggy' and so I looked at the spark plug only to reveal that it smelled like gasoline and showed it was running rich. I then tried the .36 jet with the stock e-tube and it was still running rich. I then put the stock jet back in to see if there was another factor affecting this and it ran perfectly fine. all of this testing was with a high flow air filter and a header pipe.