The best replacement for i4 is v6.

The best alternatives to i4 are rated as following:
★★★★★  v6
★★★  i5
★★★  v4
★★★  v6 engine
★★★  l4
★★  i4s
★★  h4
★★  i5 phone
★★  v6 accord
★★  v8
★  sly profit
★  v twin
★  v6 tacoma
★  i6
  3.5l v6
  v6 engines
  i2
  events

Your alternative for i4 is not listed? Suggest!
Speaking about i4, one probably shouldn't forget about fast helmet.

Other search terms related to i4 and their ratings are:
★★★★★ fast helmet
You have in mind a companion for i4 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of i4 in all years. Click on graph for more.
i4
v6
i5