[EDIT: this is pre patch, a lot of things changed, you can still get some ideas here but its not how explorer works any longer, i update it when i have time and when all the kinks are worked out in this game mode]
we all think explorer mode is about how many items you can collect
but in fact you can score far better collecting items in order
1st of how many points you get for each collected item:
colors : 3
rest : 5
in ADDITION to above points you get if you collect 3 of a kind :
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edit: 2 times hackpack's 1.5 : 45 75 90
as you can see the difference is crazy
if you got your self a magnet you can just about forget about collecting in order !
the hack packs do not influence the primary score ONLY the combo bonus!
if room is full go for item hunt, recommend BP: magnet, + maybe hackpack4 1.5
if room has 3 or less go for combo bonus hunt, recommend BP: both hackpack 2x's
example score (average scores, negative is BP-investment):
player with 2x + 2x:
collected 30 in 3 packs = 120+600 (-320) = 400
player with magnet:
collected 70 = 260 (-160) = 100
or
collected 90 = 360 (-160) = 200
the mass bonus if any on top of this !, but if there is a mass bonus then is mass bonus times score with out the (-), and so the difference is even greater, example: 720 x 500% = 3600 VS. 360 x 500% = 1800
so as you can see even if the other guys collects 3x as much, you still winning the round, and he wont even know ; )
hackpack's 1.5 are lame for combo bonus, its only useful if you like the reduced negative effects, or increased positives.. but IMO its a waste of RP as you can just avoid picking up questionmarks(unless you have a magnet), and the only really useful positive is the magnet with you can BP
this way you can optimize your always get maximum possible score
the other big advantage is that your backpack item wont get you kicked, where the magnet is considered "evil", the hackpacks SEEMINGLY not giving you an edge in winning because in the end if seems you collected less items and no one can see the 4 digit huge score, and that you where actually winning ; )
tip: you get 500% mass bonus for full room, but serpentine with only 2 you can make several times as much then if you would be top collector in a full room ; )
*this guide is not 100% complete or maybe even correct, if someone figures out more details please post !
EDIT:
as proof, this was a room with 5, i collected ONLY 56 items !
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UPDATE:
Mega Combos found:
2 red 2 blue 2 yellow/green = 72 or 144 with 2x/2x
2 nitro 2 tire = 60 with 2x/2x 140
(i know this numbers dont make sense, but this is why i got on the test, because if i get 72 or 60 with out any hackpack then with hack pack i should get a h3ll of a lot more, they dont add up)