Would the 4-2-1 or 4-1 header give better performance on a gsr swapped EG hatchback?

 

up!

 

Depends on what you want.

Often, 4-2-1 header has wider RPM range where it's good.
4-1 header can be good at high RPM but maybe it sucks at low RPM.
But even then it depends on the tube lengths to the collector, so it's not always that simple.

How about posing your question better...
"With a ???? engine, which make/type of header will help at {high/low/???} RPM?"

With some details & some understanding of YOUR goals, maybe more people will try to answer.

With a DC Sports 4-2-1 header on my '95 GSR, there wasn't much difference from the stock manifold. But it was lighter weight, and it looked better.