ATTENTION Durso standpipe wanted!

[enzo54321]

Help, Help, Please Help.

I installed my new tank not to long ago and as soon as I turned on my pump all hell broke loose, gurgling, burping, flushing, splahing was occuring in the sump and inside the standpipe, I tryed everything the u-shape pipe, submerging the pipe 2" deep, not submerging, making more holes on the Durso endcap, making them bigger I tryed for hours, days, nights I'm exausted. Some people say it's the standpipe that is too big others say it's the drain line others say I should add a valve on the return line but I'm scared with that option because of the potential flooding.
Can I get the same overall quietness without using a valve at the end of my drain line?

Please help!

Note: Durso Standpipe is 1"1/2 and a 1"1/4 bulkhead and than back to a 1"1/4 flex tube drain line under the tank to the sump bulkhead.