Sol5t1c3

i bought my 90 gxl finally, and turns out its gotta a small fuel leak on the gas tank, and i can't rev above 6000 rpms. friend of mine suggested that i use jb weld on the tank, and probably change plugs on the motor to fix the rpm restriction issue. but also i've been told i have some kind of restriction device somewhere, but i don't really know. wat ur guys' opinion and guidance? its driving me up a wall