I have a 97 328is and whenever I floor it the engine stutters heavily. When I drive normal and don't floor it my engine works perfect and I can still accelerate sorta quickly but I can't open the throttle all the way. I have no idea what would cause this and I'm very confused. I just replaced the spark plugs, spark plug boot, crankcase hose, vanos, upper timing chain and I cleaned the MAF. It only got really bad after I replaced the spark plugs and boots. Any help would be appreciated!