Well figure 6% duties and 5% gst.
Most likely none of that stuff qualifies for NAFTA(Made in USA/MX/CANADA)
You can lie but risk paying a whole lot more if they catch you then just paying your duties and tax.
Auto parts they most likely wont let you slide by but again its all up to how the officer is feeling that day.
Depending when you purchase your parts you could "fake" your stay in the states and take advantage of your exemptions.