Upgrade advice for a beginner (HELP)

[1bad89lx]

I have an 89 LX 5.0 5-Speed. It has a F-cam, Flowtech headers, Flowtech off-road H-pipe, Mac after cat exhaust, Lakewood 50/50 shocks, Mac fenderwell kit, A/C eliminator pulley and underdrive pulleys. I have some 3.73 gears waiting to be installed. This is the way that I purchased the car. I was wondering which direction I should go from here. I was thinking either a cobra intake or C&L mass air meter. If I use the Cobra intake can I use just the upper? Does that make any sense to just use the upper? I am looking to do the work myself and am not sure if I can change the lower. I wasn't really wanting to get into changing heads or anything. Also, do my upgrades warrant larger injectors? Is an adjustable fuel pressure regulator worth it with my setup?

Thanks in advance!