1995 Chevy Blazer please help

Hello we been having gas leaks around are tank so we fought out it was are desending unit we got it change then all are blazer did was chug along some time it went fast most of times it went slow very much so going a hill not enough power now it does want to start at alll its getting gas to the enginge but its not starting the blazer I must of ask a 100 people each one gave me a different answer everyone guessing the distribor cap and rotor and some people even said the fuel injectors are clod I hope you can answermy question