Back in 2007, experts advised me against using 4 tip plugs.but it still got them and later found out that i should pay heed to what the experts say
there will be no additional performance gain from 2 or 4 tip plugs, the only difference will be of new and old plugs, which itself is hardly noticable in efi cars.fuel efficiency also remains the same if the car is well tuned.the only thing these 4 tip plugs are good at is their life.u can keep them running for more then 60,000kms.i used mine for 60,000kms, removed them and put them is a friends khyber and did 35,000kms on khyber too
and the reason why im advising u against it is that they will put a lot of strain on the ignition coils of ur car which may give up after some time.so, stay away from it, best plugs would OEM ones, and if u want to save some cash, DENSO ND16 is the best one.costs 140rs/piece.