CAR - 1988 Firebird Formula 350 TPI

So it started about a week ago be driving down the road and it will miss.
The tach will jump say from 1800 to about 2400 and then back to 1800 real fast. then as the engine starts to warm up it gets worse the tach will repeatly jump and the engine starts what seems like its missing. But as soon as you let off the gas or step in to it it goes away and is fine only happens at about 10 - 15% throttle which is were cruzing is.

I thought tune up so new rotor, cap, wires, plugs, and its still doing it seem to calm down a little but went right back to doing about a day later some ideas as to what to look in to next

 

Some one has to know whats going on or maybe an idea that i can look in to this is killing my power and fuel milage im sure off it if you need more information let me know what it is ill do the best i can thanks

 

have you had the ignition module tested?

 

no i havent ... the car did this once before i did a tune up on it and it went away for a year or year and a half then about a week ago it started up again but a tune up didnt fix it this time

 

any codes? possibly knock sensor or electronic spark control. also when my fuel pump went out the car would idle just fine but when i would accelerate a little while driving it would surge like crazy