The secondaries are not computer controlled. They work exactly the same as the secondaries on any Qjet, so again the seller was clueless. There are two adjustments on the secondary air valves on any Qjet - the tension in the air valve wrap spring and the setting on the dashpot that limits secondary opening rate. The factory specs on these take into account the limited airflow needs of the 307. I would not suggest messing with them until you are SURE that the carb is adjusted per the factory specs. There are about a bazillion possible causes for poor running of the CCC system that controls the carb and distributor. A crack in any one of the eight miles of vacuum hoses on the engine will confuse the computer. A mis-connected hose will do the same. This is a very stupid computer (it's late 1970s technology) and there are far more failure modes that WON'T set a code than those that will. Here's just one example from my experience. The A.I.R. pump is used to blow fresh air into the exhaust ports when the system is in open loop mode (before the O2 sensor heats up). After that point, there is a diverter valve that switches the air to the converter to keep it from melting. On one of my cars, this diverter valve was stuck open, causing air to flow to the ports at all times. The O2 sensor saw this unneeded air as a severe lean condition and ran the carb full rich, which was exactly the wrong thing to do. Fixing the diverter valve solved the full rich problem. As for towing, the carb is the least of your problems. The 200-4R trans is the weak link.