[86GT]

Reseting the EEC is not a good idea in my opinion. You need to find the cause of the fault, not just reset it and then let it come back. If the problem cures itself or if you find the problem the code will disapear. I believe on the EEC-V systems it takes a sample of ten and if two fail it will throw the code. It keeps doing this even if the code has already been set. This is so it can unlatch the code if the problem goes away.

Do you have a tuner of some sort(Tweecer, EEC Tuner) that can datalog? If so you can do a couple of runs to find out where the 20 lean condition is occuring. If it is at WOT or so on.

Other mechanical areas to check would be a leaking EGR or exhaust manifold gasket. The exhaust gasket are the hard ones to determine. It gould be a small leak that you can not hear.

Wait a minute, I just read that it was both side. This leads me more to the EGR. The MAF element could be dirty or just plain going bad. Chargers may shorten the life of the MAF electronics due to the temperature increase. The early MAF failure thing is just my opinion.