found codes P0300,P0302,P0304 and P0306 coming up on my 2007 cadillac when scanned need help

What is your question?

take off is sluggish and engines runs rough 20mph through 40mph. Understand that these codes are for misfires. What my question is why only my even numbered cylinders?? Wondered if maybe there was an issue possibly with my engine controller. Found no frayed wires that could possibly be chafed and shorting out but i didn't find any. Help please. Thanks 2007 Cadillac CTS with a 3.6

What makes this problem better or worse?

It runs better when over 40mph.

How long has your 2007 Cadillac CTS had this problem?

A few weeks.