I never raced my E92 335i, but I have been racing and autocrossing since 2003 in a prepped honda accord until 2005, and then an EVO IX MR stock/modified till 2010, then a stock EVO X MR till the end of 2010, and now another stock EVO IX MR. The 335i's biggest problem is that it's soft. I don't agree with slowing down too much because yes it is true that sometimes you have to slow down to go faster, but that's only if you are over driving the car, not if you just aren't driving it correctly.
First turn all the traction controls off completely. The next thing I'd suggest is to learn how to control the car. Don't be afraid to get the car unsettled because that's the only way you're going to get it to rotate. Use the car's weight transfer to help turn the car, then use the steering wheel, and the gas to modulate the oversteer. Now you don't want the car drifting every turn and always being at opposite lock, but tossing the car in, and letting the rear slide a bit through a turn is a lot faster than slowing all the way down to the point that the front tires can handle it.
Try to drive the car on the rear wheels if that makes sense. The biggest thing is learning to control the car once it gets out of shape. Autocrossing is different from road racing in that sometimes you have to manhandle the car to get the fastest time out of it. It's not always about being super smooth. It depends on the course layout. If you are plowing a lot though, you need to look at your driving style before you just assume you are carrying too much speed.
Good luck at the next event!
"When everything feels like an uphill struggle, just think about the view from the top"