need everyones help with lean condition
 

im having trouble with my 89 stang its 5.0 5 speed, it has headers , offroad h pipe and flowmasters, 373 gears

the car runs really strong when its cold like when i leave for work early in the morning and pulls hard

but when the car is warmed up or its warm out it pings or spark knocks only when its warm though

i cant figure out what it is i know the car is lean the plugs were brand new and i put them in over a month ago and checked them yesterday and they look like i took them out of the box no coloring at all i bought one of those scanners from the parts store but its not bringing up any codes its saying the system is fine

if anyone knows anything or can help get my pony running strong please help

What grade fuel do you run? How much initial timing?

i run 87 but ive used 93 before didnt seem to help the initial timing is set at 10 degress

Check you fuel pressure at idle with the vacuum hose disconnected. (should read in the 34-38 range). Reconnect the hose and check your fuel pressure while under load and make sure you maintain that pressure. If not your fuel pump might be going bad. If not your injectors might be going bad.

Don't forget to check your TPS voltage. (should be under 1 volt in the .950-.999 range)
You did not put in a chip by chance right???

Start there and see what happens.

Check that the injector harness ground has not loosened. It is located between the battery and starter relay. It has a small disconnect (that looks like a fuse holder) that connects it to the main harness.

Having a poor ground will cause the exact symptoms you describe. If the car is lean enough you will notice it may start to overheat-- during normal driving!

Mike