TAG requires 30 units from a Cal CC before you apply so, you’d need to spend an additional year at a CC to make. Not to mention, you’ll need to get a really strong GPA to qualify.
If you want to go to grad school, you need a high GPA, strong test scores and some relevant experience. They won’t care if you got your BS from CP Pomona or UC Davis. Besides, you are going to find similar math requirements at the UC so, there’s really no advantage to making the switch. .
Perhaps a summer class or two in Math at CPP or a CC ill get you back on pace. If not, an extra semester at CPP is probably the best course for you to take - CPP has such a strong STEM reputation,