A couple of FYI's
1. Removing the cats will really not gain much power.
2. Even though you are exempt from inspections, you are not exempt from the requirement to have them- even US Fish & Game Wardens carry a manual that identifies each vehicle and the required smog equipment, illegal engines changes, etc with pics of how to ID.
3. Any law enforcement officer (including fish & game), EPA inspector, etc. can impound the vehicle and cite it as a gross pollutor
4. Once cited, a judge will decide if the vehicle is to be scrapped or returned to the owner- and you do not have any opportunity to speak in court- just required to sit 7 listen.
5. if the vehicle is returned- guess what, now you have to repir and take the vehicle to a federal referee station for the rest of "it's life" for a smog inspection & test.
IMHO, it's not worth the risk versus the little gain. Ok, now for muffler info....
broaderperformance.com/muffler_flow_tests.htm (Independently tested cfm flows of the more popular mufflers, glasspacks and resonators @ 15” wc:
2 ½” diameter straight pipe 521
2 ¼” diameter straight pipe 365
2” diameter straight pipe 283
2 ¼” diameter tailpipe 268
2 ¼” round glasspack- no louvers 274
2 ¼” round glasspack- with inward punched louvers 133
2 ¼” round glasspack- inward punched louvers/installed backwards 141
2 ½” inlet/outlet Dynomax SuperTurbo 268
2 1/4” inlet/outlet Thrush CVX 260
2 ½” inlet/outlet Flowmaster 2-chamber 249
2 ¼” inlet/2 ½”outlet Cherry Bomb turbo 249
2 ¼” inlet/outlet Flowmaster 3-chamber 229
2 ¼” inlet/2 ½”outlet Maremount Super C (OEM Replacement) 149
2 ¼” inlet/2” dual outlet Maremount 183
2 ¼” inlet/outlet California Turbo 229
2 ½” inlet/outlet Hooker Aerochamber 324
2 ½” inlet/outlet Hooker MaxFlow 521
2 ¼” inlet/outlet Maremount Cherrybomb Vortex 298
2 ½” inlet center/outlet offset Borla Turbo 373
http://www.popularhotrodding.com/eng...../index1.html (this is an in-depth article that tests not only the mis-conception of flow demand but also how placement of a muffler (a glass pack in this dyno test) can actually "fool " the system into thinking that it is essentially a straight pipe.
I have listed here a muffler shootout test done by CAR CRAFT:
The Mufflers
MAKE MODEL Part No. COST
SUMMIT Turbo 630125 $14.75
THRUSH Magnum Glasspack 24214 $16.50
THRUSH Boss Turbo 17718 $23.95
HOOKER Competition 21006 $25.95
DYNOMAX Super Turbo 17733 $28.50
DYNOMAX Race Magnum 24215 $31.95
HOOKER Super Competition 21106 $35.95
SUMMIT Fully Welded 630325 $38.69
FLOWTECH Afterburner 50322 $39.95
MUFFLER FLOW TEST
MUFFLER Flow at 28-in H20
DynoMax Race Magnum 528.64 cfm
Thrush Magnum Glasspack 507.40 cfm
Summit Fully Welded 343.38 cfm
Flowtech Afterburner 342.20 cfm
DynoMax Super Turbo 333.94 cfm
Hooker Competition 232.46 cfm
Hooker Super Competition 320.96 cfm
Summit Turbo 331.16 cfm
Thrush Boss Turbo 297.36 cfm
MUFFLER Idle dB WOT dB
DynoMax Super Turbo 89 123
DynoMax Race Magnum 94 133
Flowtech Afterburner 92 124
Hooker Competion 92 122
Hooker Super Competion 90 125
Summit Turbo 89 124
Summit Fully Welded 92 125
Thrush Boss Turbo 90 123
Thrush Magnum Glasspack 92 128
DYNO TEST
All mufflers were dyno-tested on a 355-cube SBC with 10.0:1 compression, Air Flow Research 190 aluminum heads, a CompCams 292 hyd. a Victor Jr. intake, a Holley 750-cfm double-pumper, and 1 5/8 Headman headers.
MUFFLER HP TORQUE 2,500-6,000rpmAverage
Hooker Competition 397.4 381.1 286.8hp/351.9 lb-ft
Thrush Boss Turbo 407.1 384.9 292.1 hp/357.5 lb-ft
DynoMax Race Magnum 409.5 394.3 298.8 hp/366.9 lb-ft
Flowtech Afterburner 409.7 391.2 294.8 hp/361.7 lb-ft
Thrush Glasspack 409.5 389.8 297.7 hp/365.3 lb-ft
Summit Turbo 411.5 386.3 291.5 hp/357.4 lb-ft
DynoMax Super Turbo 412.7 387.2 292.6 hp/358.6 lb-ft
Hooker Super Comp 413.8 387.2 292.8 hp/359.0 lb-ft
Summit Fully Welded 415.4 390.7 295.6 hp/362.4 lb-ft
While there are mufflers that will out flow a glass pack design, it also depends on the design. Does the glasspack use "louvers or perforations" - Louvers reduce the flow by as much as 50% but Allied resonators (that sell for $20-$40) each and available at any muffler shop) installed backwards in independent test flowed 90%+ of a "race spec muffler". Others using other brands consistantly showed similar results.