The Weber38 on a 82 258 does not use the EGR. With the Carter carb, vac lines ran from the EGR to the TVS on the Air Cleaner Assembly, and from the TVS to the CTO. Remove these vac lines and cap the EGR and the CTO.
There should only be one vac port on the Weber, this is where you connect the existing vac line from the distributor (hopefully it is still Tee'd to the CTO). Make sure your manifold vacuum is capped off too, you only need ported vacuum. Double check the condition of all the hoses to be sure you're not getting any leaks.
Next, set your timing. A good rule of thumb is 8* BTDC. Then set your idle screw and jets to their baseline settings by:
1- turning the idle speed screw all the way out so that it no longer toughes the accelerator cam, turn it back in until it just touches, then turn in an additional 1/2 turn only.
2- turn both idle jet screws in gently
until they just bottom out, then turn them back out 1 full turn only.
Then follow these instructions to tune for Lean Best Idle
If you're not using a fuel pressure regulator, don't drive it much until you get one or you risk damaging your float and/or accel pump and then you'll develop hard starting. If you do have one installed between a new/clean fuel filter and the carb, make sure it is set within specs (2.5-3 usually, but no more than 3.5psi). Also be sure that the fuel line remains below the fuel inlet port on the Carb. If it runs downhill to the carb, you'll get poor idle, flooding, stumbling, hesitation and hard starting.
This should get you squared away, let us know how it works out. Good luck -