Not sure if I have enough chaff grenades when I need them.
You probably need 1 for the act 4 hangar, 1 for the area right after the beast/beauty fight in act 4, 1 or maybe even 2 for the area directly after that (after going down with the elevator). And a final one for the second corridor in act 5.
You could save yourself one chaff by sneaking through the hangar. That one is quite easy. The other areas are much harder without chaff and the act 5 one isn't that bad, but you will lose a bit of health. I'm not sure, if this affects the microwave scene at all, I never died there, but maybe it will. For sneaking just enter the hangar via crawl space and not through the door. best way: go to the upper ledge in the helipad area and crawl through. Now you should be on a ledge within the hangar. Just look for the robots and jump down at the right moment. After that immediately continue onwards. You should not get spotted that way.
So that's 4-5 chaffs in total that you need.
Chaffs are:
- in act 1, IF you already got 1-2 chaffs only, just equip during the shootout sequence and walk near Johnny. He may give you some more. If you already got too many, he won't
- in act 2 in the confinement facility, in the large house right before the villa map - just go in through the door on the left side, go through another door and you will reach a corridor, turn right and go in the door to your right, which will get you into a storage room, chaffs are in there
- in act 2 in the market place with the gekkos (after the shooting segment) - they are right before the end of the map on your left inside a stall
- in act 3 but you need to go to the area, that you normally wouldn't reach at all, if you handle the resistance member properly - it's at the left upper side of the canal area, which you can access by leading the resistance member properly and then when you reached the end of this first map, just backtrack a bit up the stairs, where the resistance member walked down and there will be a path to the canal area map
- in act 4 helipad right at the start
and note: I think it's 2 chaffs per pickup. I'm not sure though.