Low burst rates again with new pc but same drives(complicated problem)

i built a new pc with only the case, dvd and floppy drives, and 2 sticks of corsair ram remaining the same. i went from asus p5w-dh/e6600 to abit ip35 pro/e8400. new power supply and cables for everything. HERE’S MY BIG PROBLEM: the burst rates on my drives are low still. They are sometimes normal, but then suddenly get low and burning takes longer than it should and transfer rates have a dip in them. I’m in DMA mode and i went into the device manager to make sure my liteon20a4p is in udma 4 and my samsung 203b is in udma 5. my previous pc didn’t have this problem until maybe a month ago. before that it burned dvd’s flawlessly for 14 months without a hitch. now the problem has carried over to my new pc. the two drives are both only 4 months old. i plugged in an older benq 1655 and same thing. what the hell do I do to fix it?