Re: Terrible milage
 

holley carbs are great, but they are very sensitive to changes in barometric pressure and temperature. to keep your truck running properly, you should check your float level and idle mixture screws on a regular basis. now that you have the truck running better, i would suggest putting a new set of spark plugs in and running the engine for a week or so and getting a plug reading. you want the porcelin on the plug to be light brown or gray. if it is darker or black, drop the jet size by 2, clean the plugs and take another reading. i think your needle and seat is fine, if it were bad you would not be able to adjust your float level, fuel would be running out of the sight hole at a rapid rate.

Re: Terrible milage
 

I have the float bowl off and pulled the float to check its condition, also pulled the needle and seat to see if the rubber tip was OK. Both items seem fine, but I found this in the bowl under the float, the holes don't line up to anything in chamber, any idea where this goes as it is not in the illustrated parts breakdown.

thanks

Re: Terrible milage
 

That is a bowl vent baffle. See attached picture for location. Can be left out of a street vehicle, is suppose to prevent fuel from entering the vent. A lot of Holley carburetor do not have this. If I remember correctly my 2300 does not have one.