Think' bout reconnecting my EGR, few questions.

There should be no vacuum at all to the valve at idle. The computer looks at tps/rpm and if it determines the car's at idle, it should direct the egr switch to not put any vacuum at all to the valve. And at every start up it looks at throttle position and re-establishes idle condition/tps setting at idle - so it thinks you're idleing even at 900. Same is true at w.o.t. - no egr valve opening. But if it's a lot better with them swapped, why not drive it that way for a while and see what happens?

Exhaust gas recirculation with efi/elec. ignition systems is one of the few emission win-win systems. Other than the clutter, there is only upside to having them work properly. The exhaust gas is inert - and since it displaces air/oxygen in the cylinder, it effectively cools down combustion temperatures. The cooler temperatures allow the computer to add more timing and less fuel when the egr is open - which makes for better fuel economy and lower emissions. The downside as you and others have discovered is that if you disable it - without turning off the egr function in the ecu (chip or tweecer required) the extra timing and lean mixtures the computer orders up at part throttle because it thinks the egr is working often cause detonation.

The cannister should be connected to the fuel tank vent line -- so that when the purge valve is ordered open by the ecu, it allows engine vacuum to 'suck' on the fuel tank vent line through the cannister. Fuel tank to cannister, cannister to purge valve, purge valve to intake manifold. I should clarify - that's how mine's hooked up, and I think it's functionally the same as the Stang.