987 Airbox-Worth it?

[Nitro V8]

Old thread revival!

I have collected all the parts together to do the 74mm tb conversion on my 2003 facelift s.
74mm tb, 996 plenum, 80mm silicone and Ali tubing, various jubilee clips.
I also have a modified 987 airbox and 987 maf tube and maf.

A few questions to those in the know
1) Will I still get improvement in power by fitting the 74mm tb and 996 plenum but retaining the 986 airbox and maf?
2) If I fit the 987 airbox do I need to fit the 987 maf or will there still be benefit if I retain the 986 maf tube?
3) If I fit the 987 maf does it definitely need a re flash to make it run correctly and not throw a cel?

Thank you