Hi I just ordered a flex helix uppipe and downpipe so I have the following questions.

1.Should I be worry free as long as I install the pipping with new gaskets? epsecially the one that came with the uppipe (I ordered from gruppe-s btw)

2. having my car catless soon, should I Be cocern if my car will run too rich or lean because im fooling the o2senors on the ECU? and if so should I monitor or can I leave the ECU stock setup?

3.In the future if I install aUtech chip, do I need to reconnect my 02senors back to the ECU?

4.How hard is it to install the uppipe, I do not think I will do it myself but if it takes all day at a shop that would cost me too much money. I just want to find out how long apprx it takes so the shop dude wont rip me off in labour =]

5. how much gains would I notice from going catless with helix pipping I also have tanabe hyber medal cat back exust.. 250hp? 270? I notice turboxs with their turbo back they claim to gain 26.5 hp to the wheel and that is without uppipe.