First off, sorry for all the recent posts asking questions, but this one still has me stumped. Here are the symptons... after a few pumps on the accelerator, the car starts normal , warms up and gets to a nice idle, drives on local roads with no problems, changes gears, dosent die on hills anymore and seems to run great! But once I get it onto the highway, I can accelerate up to 70 with no problems and hold that speed there, then after about 5 to 8 minutes, the car just looses power (like I took my foot off of the accelerator). It will lose power for about three seconds then the power will come back for about three to five seconds, then lose power again for about three seconds and keeps repeating. As it continues to do this (my foot has not lifted off the pedal at all) I'm lucky to be doing 45 mph. I get off on the next exit ramp, and as long as I'm doing local road speeds. (0 - 50 MPH) everything seems normal like there was no problem at all.
Things that I have done.
New Fuel Filter
New second stage diaphram on one carb. (the other diaphram was in good shape, thanks for the help kavadarci!)
Sync the carbs using the hose in the ear meathod, which seemed to be pretty close. (I was trying to find a flow meter with no success)
new air filter
Things that I was thinking of doing (not sure if it will help)
Install a new coil
Install a new rotor cap and rotor (the one in there now has not really been used, but it has been sitting on the car unused for about 10 years.
Install new spark plug wires. (the ones that are on there now had some minor shielding that was exposed. I covered these "exposed" spots with silicone.
Thanks for any insight and advice, as I am starting to lose my mind.