i have everything i need to make my boost leak tester except for the PVC cap. the guide says i need a 1.5" PVC cap, but the cap i bought is too small for the 2.5" coupler. i went to Lowes and Home Depot and the only PVC caps i found were the black ones and i'm not sure if those are the right ones. i bought a 2" cap as well, but that's a little too big. is the correct PVC cap on the homedepot or lowes website? if so, can someone send me the link so i can just show it to someone at the store?