I test drove a wrx the other night and he told me that the o2 sensor was misreading the info because he had turbo catback exhaust. The check engine light was on so I asked and he said becasue the resonator and something else was taken out. I really loved the car, but I am not to sure about that part.
Sounds like he took out the catalytic converters and that is why the engine light is out. If you live in a state where you need to pass emissions test when you register the car under your name then don't buy the car. The WRX comes with about 6 catalytic converters and they will be expensive to buy when you have to pass the smog test cause it will not pass without them.
If you drove the car and the axles did not clunk or make noise the car should be ok, since those have a tendency of breaking when raced.
ECLIPSE/TALON NONE TURBO 2G DSM STAINLESS STEEL CATBACK CAT BACK EXHAUST MUFFLER, 3" PIPE FULL STAINLESS TURBO/CAT/BACK EXHAUST+HEADER+DOWN PIPE UP PIPE TURBOBACK, SINGLE PATH 4.5" TIP TURBO/CAT BACK+DOWN+UP PIPE EXHAUST 02-07 IMPREZA WRX/STI, DUAL 4" MUFFLER TIP DOWNPIPE+TURBO/CAT BACK CATBACK EXHAUST 91-99 3000GT VR4 GTO, 95-95 ECLIPSE GST TURBO 4G63T STAINLESS CATBACK EXHAUST, 1995-1999 MITSUBISHI ECLIPSE 2G 420A NT NON-TURBO 2.5" CATBACK EXHAUST SYSTEM, Walker Exhaust Exhaust System Super Turbo Cat-Back Steel Ford Ranger 2.3 3.0, STAINLESS STEEL 4.5" TIP DUAL MUFFLER CATBACK EXHAUST SYSTEM MR2 MR-2 TURBO W20, 3" ALL THE WAY SS TURBO/CAT/BACK EXHAUST SYSTEM DOWN-UP PIPE CATBACK TURBOBACK, Walker Exhaust Exhaust System Super Turbo Cat-Back Steel Natural Toyota 2.7L Kit, ECLIPSE NT GS RS 2.0L S/S 2.5" INLET CATBACK EXHAUST SYSTEM NON TURBO, 95-99 ECLIPSE GST 3" TURBO 4.5" TIP N1 CATBACK EXHAUST MUFFLER w/SILENCER, 97-98 240SX S14 SR20 TURBO 3" DOWNPIPE EXHAUST CATBACK FREE SHIPPING, 89 90 91 92 93 94 S13 TURBO 3" DOWNPIPE EXHAUST CATBACK FREE SHIPPING, Walker Exhaust Exhaust System Super Turbo Cat-Back Steel Ford Mustang 3.8L Kit, 1991-1997 Dodge Stealth R/T Turbo m2 Cat-back Exhaust, MAZDA 10-11 MAZDASPEED 3 TURBO STAINLESS STEEL DUAL CATBACK EXHAUST SYSTEM 2.3L, 3" ELECTRIC EXHAUST CUTOUT CATBACK TURBO SYSTEM KIT! STI WRX EJ20,25 GDA GDB GC8, 95 96 97 98 Nissan 240sx Catback Exhaust 1995-1998 S14 N1 SS 3" Turbo, Megan Racing Exhaust Turbo Type Catback 89-94 Eclipse/Talon AWD, Megan Racing Exhaust Turbo Type Catback 99-02 VW Golf/Beetle 1.8T/2.0, Megan Racing Exhaust Turbo Type Catback 95-99 Eclipse FWD, Megan Racing Exhaust Turbo Type Catback 95-99 Eclipse GST (3-piece), Megan Racing Exhaust Turbo Type Catback 02+ Subaru Impreza WRX, MEGAN RACING CAT BACK EXHAUST 95-99 ECLIPSE GSX 2DR HB 2G D33A AWD 4WD 4G63 ONLY, MEGAN RACING CAT BACK EXHAUST 90-94 MIT. EAGLE TALON TSI 1G AWD 4WD 3" 4G63 4G37, MEGAN RACING 3" CAT BACK EXHAUST 95-99 MIT. ECLIPSE GS-T 2G DSM D32A 4G63 ONLY, MEGAN RACING CAT BACK EXHAUST 95-98 MIT EAGLE TALON 3DR TSI AWD 4WD 2G 2.0L 4G63, MEGAN SHORT TIP CAT BACK EXHAUST 95-98 NISSAN 240SX S14 SILVIA ZENKI KOUKI SR20, Megan Racing Exhaust Turbo Type Catback 08+ Chevy Cobalt Turbo (Blue Tip), Megan Racing Exhaust Turbo Catback 95-98 240SX S14 KA24DE/SR20DET (Short Tip), Megan Racing Exhaust Turbo Type Catback 95-98 240SX S14 KA24DE/SR20DET(Long Tip), WRX/STI 3" TURBO/BACK OVAL/OEM CATBACK EXHAUST SYSTEM +20HPS CAT BACK RACE/DRIFT, 2010 2011 Mazda Mazdaspeed3 Dual Catback Exhaust System 4.5" Tips 2.3L Turbo , MITSUBISHI EVO-8-9 03-08 LANCER STAINLESS STEEL TURBO CAT BACK EXHAUST SYSTEM, 03-05 DODGE NEON SRT4 DOHC TURBO STAINLESS STEEL CATBACK EXHAUST SYSTEM+DOWNPIPE, IMPREZA 02-07 WRX STI EJ25 STAINLESS STEEL TURBO CAT BACK EXHAUST SYSTEM+UP PIPE, 95-99 ECLIPSE GST 2.0L TURBO N1 CATBACK MUFFLER EXHAUST SYSTEM, 2010 2011 Mazda Mazdaspeed3 Dual Catback Exhaust System 4.5" Tips 2.3L Turbo , SINGLE TIP STAINLESS CATBACK EXHAUST 95-99 TURBO MIT ECLIPSE GST EAGLE TALON TSi, 2002-2006 SUBARU IMPREZA WRX STi TURBO 2.0L 3" CATBACK EXHAUST SYSTEM 03 04 05, 4.0" N1 TURBO CATBACK EXHAUST SYSTEM 2004-2008 SCION TC, OBX Catback Exhaust JDM 94-99 Celica GT4 ST205 Turbo, 3" exhaust catback turbo electric e cutout valve 350z s13 s14 sr20 300zx vg vq, OBX 3.5" Catback Exhaust System 93-98 Toyota Supra 3.0L Twin Turbo 2JZ-GTE JZA80, 95-99 DSM ECLIPSE 4G63T N1 TURBO CATBACK EXHAUST SYSTEM, SUBARU 02-07 WRX/STI TURBO TITANIUM TIP CATBACK EXHAUST, 1989-1994 MITSUBISHI ECLIPSE 1G GSX TURBO CATBACK EXHAUST 4G63, 3" TURBO CATBACK EXHAUST SYSTEM 94-01 ACURA INTEGRA GSR, m2 1986-1992 Mazda RX-7 RX7 Turbo FC3s CatBack Exhaust,