can we stop with the MBC are the devil ideas. MBC is the devil if you dont understand your car and you cant use it. I had a mbc on my 03 wrx for 18 months with up/dp/catback and i would make sure it only hit 17psi in 5th gear. I would beat cobb stage 2 wrx's off a roll and off a stop too. I would even trap higher then they would at a drag strip. Best 60 dollars i ever spent for that car. If you have an 02/03 bugeye its a perfect mod if you just know how to use it. I even dynoed my car and a/f was fine. Nothing even close to dangerous. As long as your catless and you have an 02/03 its perfectly fine. JUst dont overboost, all your doing from the sounds of it is hitting limp cause your overboosting witht he mbc. Just get a boost gauge and make it so 4th gear it only hits 16 psi which means it will hit like 16.5-17 in 5th and you'll be fine.