2.4 manifold

hi guys , i bought a 2.4 manifold from a Chevy Malibu :)
1-Does anyone knows what more parts it requires on a astra g cabrio (z22se) from Germany ( I don't know if i got the 100 amp alternator, can someone help me with this? )
2- Does it will make a nice improuve to bhp with a remap? ( i got a bigger exhaust manifold)
 
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