Getting 19 points of Armor (which requires FBA+Helmet+Augmentation/Troll or AJ+Shield+Augm./Helmet/Troll) is really important for one big reason: It lets you take the HE damage as stun when it's a direct hit. Of course depending on how the GM does dodging blasts, it might not be that bad, but yeah, it's nice to have.
Chunky Salsa is rather easy, really. Assume most corridors are 2m wide. If the grenade explodes at your feet, it mashes into the walls at 14P/-2. For a plascrete wall this ties with the 16 Armor rating so it is Physical damage. Roll 10+16-2 dice (avg. 8, 6 when buying hits), if the remaining damage does 10+ damage the wall breaks. We're talking 6% when rolling and 0% when buying hits, so assume the Plascrete holds and bounces. That puts you at 16+12x2+8x2+4x2=instakill.
Now imagine the grenade explodes 1m in front of you. Blast doesn't bounce that much for you (since we're only dealing with 4 dimensions bouncing), so you just take the 14P/-2. Unless you're in a corner and got the wall 1m behind you. Then it's 14+10, so 24P/-2 damage. This is going to hurt and only the biggest Tank character will be able to reduce this to Stun.
Let's assume a 6x6 room. Grenade explodes in the center, player is 1m removed from the wall. Blast in his direction goes 2m, hits for 12, 1m, bounce, 1m, hits for 8, doesn't reach the other wall. The other wall is 3m, then 5m to the player, so 8m distance, this means the grenade does 0. 20P/-2 damage. A frag grenade goes 2m, 3m+1m, 3m+6m+5m, 3m+6m+6m+1m, so 16, 14, 4, 2 for one side. Other side goes 10, 8. 54P damage. In a room of 10mx10m it'd be much less.
The numbers are easy. Talk in meters, take the distance, reduce damage with 2x that for HE and 1x that for Frag. Yes this means that in an enclosed environment, fragmentation grenades are actually more lethal. HE grenades are cute but the frags do more damage at a distance. And if the space is rather small, you can just kill off the character.
So for instance 16 damage bounce off a wall 2 meters away 12 damage the other wall at this point is 5 meters away 2 more damage. So for three walls this would be 16+36+6. All done at the same time. This is excessive and these are not the full rules I'm using it should actually do more.
16 damage bounces 2 meters away, 2 meters back, it becomes 8 when it hits you. It becomes 0 later. Yes, with three walls we're talking 16+8x3=40P, death. Grenades are lethal when used in an enclosed environment.
I do agree that Chunky Salsa IS rather much now that grenades actually do decent damage. After all, they reduce at the same rate but have a far greater base damage, so do much more damage. Even a single wallbounce already puts the damage at 100% lethal. So why not use the overlapping explosions rule instead of the chunky salsa rule? In other words, don't just add the reduced damage, instead half additional damage and improve the AP instead. This means that if the frag grenade explodes 2m away and the wall is 2m behind you, you don't take 16+12 = 28P/+5, but instead take 16+12/2=22P/+4.