I have the SCP 2.1/4" downpipes with high-flow cats and, the Flowmaster Force 2 resonator pipes will slip inside the downpipes ok. However, even though the resonator entry pipes are expanded to fit over the stock 1.7/8"-2.00" downpipes it still leaves a small gap of about 1/8". I had mine cut and welded by a local shop, but you could either fill the gap with some sheet metal & then clamp it or preferably cut the resonator pipes and use small exhaust adaptors (unfortunately you'd then have 2 adjacent clamps). The SCP pipes are also unequal length, so one side slides right over the resonator pipe & the other barely overlaps. If I did it again I'd have the exhaust shop cut and weld adaptors on, to smooth out the flow. Nevertheless I think they are a great improvement & if you are also skipping the cats (trust that's ok for your State inspection) I think you'll like the sound. You might also want to check out TexasThunderbirds, as he sells downpipes without cats a lot cheaper than SCP.