Bmw is 6cyl , 2.5L has stainless steel exhaust, intake, and performance module.
Nissan has exhaust, headers, and intercooled turbo engine 4 cylinder.
Its really a toss up. Are either cars manual? Who knows if the aftermarket parts on either car actually helped, or hindered the cars. In some cases, headers and exhaust actually hurt the torque and horsepower in the lower RPMs, but help in higher RPMs. If that is the case, the turbo 240sx would probably win. BMWs aren't built for drag races, but in a circuit track, I'd take the 325.
02-06 NISSAN ALTIMA V6 DOHC SE 3.5L VQ35DE STAINLESS STEEL RACING EXHAUST HEADER, JVT RACING STAINLESS STEEL PERFORMANCE HEADER NISSAN 90-96 300ZX Z32 NON TURBO, STAINLESS RACING MANIFOLD HEADER/EXHAUST 02-06 NISSAN ALTIMA 2.5L I4 L31 QR25DE, STAINLESS RACING MANIFOLD HEADER/EXHAUST 91-99 NISSAN SENTRA/200SX GA1 SE/XE/GXE, STAINLESS STEEL EXHAUST HEADER 02-05 NISSAN SENTRA SER SE-R B15 2.5 4CYL SR20DE, NISSAN SENTRA SER/SPEC-V 02-06 2.5L DOHC STAINLESS STEEL HEADER/EXHAUST SYSTEM, T-304 STAINLESS STEEL EXHAUST HEADER 03-06 NISSAN 350Z G35 FAIRLADY Z Z33 VQ35DE, STAINLESS MANIFOLD HEADER+DOWNPIPE 91-94 NISSAN 240SX/180SX S13 SILVIA KA24DE, STAINLESS RACING MANIFOLD HEADER/EXHAUST 02-06 NISSAN SENTRA 2.5 SER SE-R SPEC-V, 91-99 NISSAN SENTRA SE XE GXE 94-98 200SX STAINLESS STEEL EXHAUST HEADER 1.6L, STAINLESS STEEL EXHAUST HEADER/MANIFOLD 95-98 NISSAN 240SX S14 SILVIA KA24DE KA, STAINLESS STEEL EXHAUST HEADER 91-99 NISSAN SENTRA 200SX 1.6 4CYL GA16DE B13/B14, T304 STAINLESS STEEL MANIFOLD HEADER/EXHAUST JDM 03-06 NISSAN 350Z INFINITI G35, STAINLESS STEEL MANIFOLD HEADER/EXHAUST 02-06 NISSAN ALTIMA 3.5 V6 VQ35DE L31, STAINLESS STEEL MANIFOLD HEADER/EXHAUST 91-99 NISSAN SENTRA/200SX GA1 SE/XE/GXE, NISSAN 350Z/INFINITI G35 Z33/SKYLINE STAINLESS STEEL HEADER/EXHAUST JDM RACING, NISSAN 240SX 89-94 S13 KA24 S-13 STAINLESS STEEL HEADER/EXHAUST SYSTEM DRIFT JDM, 90-96 NISSAN 300ZX Z32 NT 3.0L HEADER CATBACK EXHAUST, Header Stainless Steel Piping 45° 3"& 2Coupler&4T-Bolt Nissan 240SX S13S14 350Z, Header Stainless Steel Piping SST201 45° 2.5"16 Gauge Honda Civic Acura Nissan, Header Stainless Steel Piping 45°2"& 2Coupler& 4clamps Civic Nissan 240SX S13S14, 95-98 NISSAN 240SX S14 SILVIA KA24DE SE/LE STAINLESS EXHAUST CHROME HEADER+O2, Stainless Steel Header Nissan 300ZX 1990-93 94 95 96 TT, Megan Stainless Header Nissan Sentra 91-95 96 97 98 99, STAINLESS RACING MANIFOLD HEADER/EXHAUST 95-99 NISSAN MAXIMA 3.0L V6 A32 VQ30DE, 02-06 NISSAN SENTRA SER SE-R SPEC-V 2.5L 2.5 T-304 STAINLESS HEADER EXHAUST JDM, STAINLESS STEEL RACING EXHAUST HEADER 02-06 NISSAN ALTIMA 3.5 V6 VQ35DE L31 JDM, NISSAN 91-99 SENTRA B13 B14 200SX GA1 GXE SE XE STAINLESS STEEL EXHAUST HEADER, STAINLESS STEEL SS RACING EXHAUST HEADER 02-06 NISSAN ALTIMA 2.5 4CYL L31 QR25DE, NISSAN 02-06 ALTIMA V6 VQ35 STAINLESS STEEL HIGH PERFORMANCE EXHAUST HEADER 3.5L, Stainless Steel Header Nissan 300ZX Z32 90-96 NA 3.0 V6, 02-05 NISSAN SENTRA SER SPEC V 2.5L DOHC STAINLESS EXHAUST CHROME HEADER+GASKET, NISSAN ALTIMA L31 VQ35DE 3.5L V6 STAINLESS EXHAUST CHROME HEADER+GASKET+BOLTS, 91-99 NISSAN SENTRA B13/B14 94-98 200SX BASE/SE STAINLESS EXHAUST HEADER+GASKET, NISSAN 240SX S13 SILVIA KA24 STAINLESS EXHAUST CHROME HEADER+DOWNPIPE+GASKET, STAINLESS RACING MANIFOLD HEADER/EXHAUST 02-06 NISSAN ALTIMA 3.5 V6 VQ35DE L31, NISSAN 350Z/Z33 FAIRLADY INFINITI G35 VQ35DE V6 STAINLESS EXHAUST HEADER+GASKET, 89-94 NISSAN 240SX S13 SILVIA KA24DE STAINLESS STEEL EXHAUST HEADER+DP DOHC 2.4L, Nissan Pulsar GTiR GTI-R RNN14 SR20DET Stainless Steel Exhaust Manifold Header, STAINLESS STEEL MANIFOLD HEADER/EXHAUST 95-99 NISSAN MAXIMA 3.0L V6 A32 VQ30DE, 2002-2004 Infinity G35 Nissan 350z m2 Performance Stainless Steel Header, PERFORMANCE STAINLESS STEEL HEADER & DOWNPIPE '89-94 NISSAN 240SX/180SX KA24 S13, Stainless Steel Header Nissan Maxima VQ30DE 95-99 V6, T304 STAINLESS STEEL NISSAN 240SX S14 /S-14 KA24 SS JDM HEADER/EXHAUST/SYSTEM , STAINLESS STEEL HEADER NISSAN 240SX S13 89-90 OBX , OBX Header 02-05 Nissan Sentra 1.8L Stainless Manifold, Borla 17221 Header Nissan 3.5L Stainless Steel, 02-06 NISSAN SENTRA SER SE-R SPEC-V 2.5L 2.5 T-304 STAINLESS HEADER EXHAUST JDM, NISSAN 240SX 89-94 S13 KA24 S-13 STAINLESS STEEL HEADER/EXHAUST SYSTEM DRIFT, Megan Stainless Header Downpipe Nissan 350Z 02 03 04 05,