i put fenton on my 235/3100 last summer and am well satisfied. the ports are to add a heat riser plate to take the place of the orginal one. lamgdons stovebolt on the links page have the plates already made up. i got my fentons from patricksantiquecars.com. the heat plate keeps the truck from stumbling when cold but i have had little trouble with out it and drove my truck in the snow and 9 degree weather over christmas. i did have a little stumble this week when it was about 30 degrees and rainy. ron
