im driving what used to be my mom's 1991 Nissan Sentra II, 1.6L, ECCS, DOHC. yung supersaloon na automatic (see matic pa? definitely not for racing! hehe ) im more of a city driver pero twice a month, im using NLEX or SLEX...
am sure ghosthunter would disagree with this... he had a blown sentra matic before...

1. where to get headers? someone reffered me to CPM Mufflerhaus, ok ba yun? ano yung Nodalos? ano yung mandrel bends, etc.? how much usually and cost plus installation?
try to get mandrel bent headers. they have smoother "bends" than regular ones.

2. where to get and what to get, intake system. is SIMOTA ok? i think KNN is better, pwede bang Simota ang tube tapos KNN ang filter? ano benefit ng cone-type sa drop-in-airbox type? how much usually?
cone-type... better airflow! but be wary where it is placed since you want cold air to be sucked into your engine rather than hot air coming from your radiator fan (which'll just negate the better airflow).

3. anyone here my experience with fuel savers like KHAOS, etc.? what about yung kinakabit sa fuel lines? effective ba mga to?
just a bunch of BS.

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btw, try to do your mod one at a time... like install first a new air filter... after a month headers... then freeflow mufflers... etc...