here a bit i take from a celica forum....
1st and 2nd gen 3SGE incorporate the TVIS system it wasn't until the 3rd gen they eliminated the TVIS. 2nd gen utilizes a dual plenum design IIRC. Also there was a 160HP 1st gen 3SGE designated 3SGE(LU) high output. It used a higher compression piston to achieve the higher output HP and a more aggressively tuned ECU. FYI if you go with a 1G 3S get the 2G 3S exhaust header, small port, long runner design and if you opted for the 2G 3S use the 1G 3S larger port, short runner exhaust manifold.