Best ecu ground source for electronics (BCC and VPC)

Hey guys, i was wondering if you could tell me what the best ecu ground source is to connect a greddy bcc and hks vpc? Should i use Wire E1 or E2 off the ecu?

create new ground to metal chassis

Is that really the best way to ground those electronics? What has everyone else done? E2?

all grounds will lead to metal chassis, so tapping into another ground will only lead to the chassis anyway.
Why not reduce the potential for increased resistance along the ground path going via E2 and go straight to the metal of the car?

You should ground all electronics at the same point, soldered to individual lugs, or, at the very least, use the same ground wire that the ECU uses assuming it's capable of the current. Grounding to the chassis risks changing reference levels across each component which could drive current in reverse and/or exceed allowable potentials in one or other part. For fairly low current devices use the signal ground, for stuff like 02 sensor heaters use the power ground.