For drop in filter you do not need any extra modification, just drop it in like your OEM filter and you are ready to go.

As for open pod a.k.a. mushroom type filter, a lot of things need to be taken into consideration to extract the full potential.
You need to install a proper heat shield to shield the filter from the heat generated by the engine, if not the air filter cannot be run at its maximum capacity.

Final consideration is that how much you willing to spend and what is the gain in horse powers you looking at

OPen pod provide higher air flow to engine, while drop in is lesser.
but the air flow noise will be loud if using open pod......

for performance increase, open pod is better choice
but you said 13-14BHP increase, i think is too difficult........

where u get the figure adding 13~14BHP?
i think it add barely 5hp

13-14 hp is too much man ... i dun think that is possible...

nope.... drop in is around 2- 4 while open port should be 5 - 8... 5 - 8 also depends how u set up ur open port.... if u suck more heat rather den cold air which is also useless...

Some Open Pod Air filter will harm your engine. While I heard some said that, K&N Drop In Air Filter also can work well as those open pod air filter. Open pod air filter will cause FC increase a little bit but more power. I wanna change to open pod air filter, but the SC don't give me change cause will void the warranty. Cause those open pod air filter sucking more air that stock drop in so it will harm the engine.

once you got open pod....you mod will be go on to get full potential of the open pod.

it's like PC, if your motherboard is cacat but you got super cun display card, the display card can't performed at full potential. So you must upgrade motherboard, then later need to add Ram then bla bla bla...the list goes on...

hahaha.... actually both is the same lar... both using the same filter element... jz that how it mounts and so on...

open-pod
ppl say it FREES UP (not give) more horses because at high revs, the air flowing in is not restricted by the shape of ur airbox.... thus, u'll get smoother revs at high revs...
but the disadvantage of it is, it is exposed to the hot temperature in ur engine bay.... this can be solved by using heatshield and cold air intake...

drop-in
direct replacement into ur airbox... thus, all the factory setup cold air intakes and snorkle can reuse again.... good, no need headache go do heatshield and cold air intake adi.... but at high revs, its kinda restrictive due to the limitation of airflow inside ur airbox....

applications...
if u want to go further in car modifications.... if ur driving style is mostly at moderate n high speed... try go for open-pod....

if u jz wan abit increase in horsepower and ur driving style is around town area with lotsa low speeds and stop-go, use drop-in....

ok??...

open pod, u try getting stuck in KL jams on a sunny day and see


or try going thru flash flood areas

with unmod engine, open port filter also wont give u extra power till can feel the difference, just some extra sound. during hot day, ur car may become more sluggish. open port also wont make ur car consume lots extra petrol.if u wish to go for open port, make sure it to get it done with proper heat shield and CAI.

the pros of after market drop in filter is washable & the element look nicer than oem 

On my experience on installing the drop in into my myvi (blitz sus air filter) does makes an improvement to my car, with better throttle response at lower rpm due to improvement (although minor) to the torque.

Unless if u really want to improve low end power, i suggest u go for an extractor change rather than air filter. 4-2-1 extractor will definery improve the low-mid range power.

lower fc not much noticeable for me.coz when u changed ur filter,u'll intended to floor ur pedal more.haha...

I knoaw only 2 open pod that can be washed. K&N and Blitz's SUS

as far as I know cannot la. After awhile must change the filter

my car(old iswara) jus changed 2 k&n drop in.. it actually give more lower end torque n betta throttle response.. lower fc.. the diff is noticeable.. worth it..

before it was full tank for 300+km den after installed d k&n drop in is around 330+km (city drive).. it even better when drivin on highway!

my fren... there r so many brand u can think about...
k n n... hks....zenden... depends on you la...
drop in filter brings higher air flow than ori 1...and can tahan lama...
and looks cool... red...
so far... ur gti now become a monster oredi....
     
i n biscuit cannot follow ur gti liao lo....

k&n would b the better choice cuz its reuseable.. hks has d performance but bad filtration n cant last long.. correct me if im wrong.. hehe

i read in an article, actually drop in filter wont give u extra hp or torque gain. Since u just put in the filter box, it still remain as restrictive as before, the slightly better flow of filter wont let u gain much. open port still way to go with proper heat shield and cold air intake.