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Basic Engine Modifications Guide for BMW E30 M20 Performance Engine Chip- Simple, effective and inexpensive Free Flow Air Filter and Heat Shield – This is an effective and simple modification. Not much good without a heat shield. Larger Air Flow Meter – Very effective. The 3.5 liter air flow meter is much larger than the 325I meter. It can be used directly. However, most cars will not idle very well useless you replace the board in the 3.5 unit with the board from your 2.5 liter.

Buy a new meter to throttle body rubber boot, warm up the end and stretch it to fit the 3.5 unit. Higher Flow Injectors – Effective with other mods. Actually this is an important addition if you have substantially increased HP.

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