Sorry to be a pest, Lancer... Just wanted to let you know that you were right on with this one. The 155main and 1/2 spacer seem to be working really well, and because my muffler was so  annoyingly loud, I welded the straight-thru port on it shut and left the baffled side open. MUCH quieter, less back firing, and now the 1/8 - 1/4 throttle response is better. I'll run a couple of tanks through it to see how everything looks. Right now I'm still at 49 mpg. THANK YOU for all the help.