OK, let me see if I can clear up a couple of nagging questions I have? I did the tune from Eurocharged, I got a whopping increase in performance (USING MID GRADE 89 OCTANE). I use the mid grade at 89 because it is 2 points below the 91 octane required. Since all the stations around here use 93 octane premium, I cannot use the 91 it says it requires. If the car can adjust 2 points below the 93, then I figure it can adjust the 2 points down from 91 to 89. This is not a octane post, just stating this point before I post my quandary with anyone installing the 74mm TB and MAF housing. I wonder if the car can adjust to the 74mm TB AND using something lower than 91 octane? You are injecting a whole lot of extra air and if you do not adjust the tune for all that extra air, you may be super starving the engine if you use anything less than 91 octane. Now I know I am using 89, but I have the tune for the TB/MAF so I am thinking I am air/fuel neutral again given the tune should be balancing the A/F ratio again so the 2 points up/down semi rule should be OK. Now you know my stand, and here is my question stated for others. If you use the 74mm TB/MAF, are you putting the MINIMUM 91 octane, or are you also saving $ by using 89? I suggest if you are, you may be seriously lean! OK, now please lets not jump on my assertions about my XF and 89 octane, lets find out who might be doing the mods and not using minimum 91 octane (before getting a tune). OK?