Mazda B2600i setting new rev limit

I have a b2600i '91 and i want to raise my redline to 6k, its a sohc 12valve fuel injection motor. Currently the limit is at 5.5k, but the b2200 has a 6,000 redline. I know its not recommend to go into the red but i was thinking with the proper ignition and rev limiter (msd 6t and soft-rev controller). what do you guys think about that. Also my truck has about 88000 miles on it and i was wondering if i should replace my mass air flow sensor and oxygen sensor?

thanks
~alivak