i have a 1985 c-10 5 liter and i want to put some headders on it but my dad says that on my truck headders well improve nothing if not decrease performance because he says there has to be someback pressure is he right or just saying this so i dont spend money on my babe?

well they are a lot of work and maintenance .and it is true that you some back pressure ,if all is stock the true benefit is for performance and usable power ,header's tend to rust out relatively quick and have gasket leak"s (personal experience )they can be good or bad !

ok thank you very much and i forgot to ask but i think i have the answer, is it ok if i cut off my muffler and just make it straight pipe? cuz i cut off the catalizer a while ago to make it sound better but if i also cut the exhaust off well it be bad due to no back pressure?

well i think you answered your question ,you have to have some back pressure not to mention no muf and cat johnny law will be hounding you !!!!!!!!!!!!!

That depends on you. This headers don't cost that much, if you want them to be stucked in your exhaust. Any parts have their own purpose and say, try this Ansa header pipe (http://www.carpartswholesale.com/brand/ansa/ansa_header_pipe.html). some of my friends have them but no one got bad experiences.