what kind of hp difference will i find?? and what type of each should I buy for a stock engine that will be modified shortly??

 

If any of those are bad u will feel a difference but if there in working order you will not feel any difference

 

the stock coil is good, plugs and wires should be changed every 60k or so

if you are going to go the nitrous route you will want to go with non-platinum spark plugs with a colder range then stock (correct me if I'm wrong) and some choose to go with aftermarket ignition as well then