The ACT is just a thermistor - responds pretty quickly to temp changes. Put an ohmeter on the terminals and grab the thermocouple junction to see. What I wonder about is how much radiant (sun) heat afects the reading as there is more heated mass (radiant source) around the ACT mounted runner than the plastic intake - assuming the car is running and air is flowing through the engine bay. Could this be the difference? Lots of variables.
I did the same thing as Michael (relocated to the air tube). I just made a round hole in the tube right ahead of the tb and popped it in. Napa makes a really nice black plastic version of the ACT that though more expensive, really looks slick AND keeps that area from looking like the space behind your toilet with that UGLY brass fitting. Michael, with all of the debate about this changing computer parameters and such, I'm wondering if this may not in some way be related to the gas-mileage issues I wrote about in an earlier thread? I'll ask this in the other thread as well if appropriate.
The ACT for mine is located in the stock air box, 1 1/4" down from the upper front corner and 1 1/4" back from the front edge.
I have no complaints about the gas mileage at this time. I commute 52 miles a day and fill up with 12.75-13.25 gallons once a week. That is the same as I was getting before I did the Explorer manifold swap.
I just filled up last night - my 10th straight 19+ around town tank; mine gets 24-26 on the road. If all else is working correctly, I'd look elsewhere for a gas mileage issue. If it were running that rich (so bad gas mileage were the symptom), either the O2's would pick it up and the ecu would correct it, or you'd get a check engine light indicating a problem it couldn't correct.
tmoss - my sense is that any sort of radiant heat issue might show up during hot or cold starts - but once significant air is flowing over the business end of the sensor, I don't think things would be greatly affected.
thanks for all the info, i think i'll like it here on this site. does anyone make a elbow to bolt down on a regular 4 barrel intake? i know i would have to weld in the bungs for the injecters (i'm a welder), but i would love to be able to use a victor jr intake with the fuel injection set up. it has speed density on it now, so i guess before i do anything, i'll convert it to mass air. will that be a beyatch or what? thanks every body