dahdi_test result - increase accuracy

i’m using a tdm410 card, with 1 fxo and 3 fxs and vpma32 echo cancellation module.
I’ve done dahdi_test and i had an average accuracy below the 99,975%.
Best: 99.996 – Worst: 99.897 – Average: 99.959463

I tried increasing latency adding “options wctdm24xxp latency=128” to /etc/modprobe.conf file.

I tried disabling acpi daemon.

I tried disabling floppy, sound card, ide channel, parallel and serial ports.

How can i increase accuracy?