I've been working on my truck for a few weeks now making progress and repairing and replacing i've gotten code 998 and 122

However when i start the truck the CEL comes on runs fine but it will rev up real hard then drop quickly will not die but will slowly return to normal running idle i'm a first time ford f150 owner and before this issue the CEL would only turn on at 65 mph any slower it'd shut off....i hate to admit it but i need help :p

 

Check the wires to your TPS, clean the connector.

What Year?
What Engine?

 

whoops sorry 1995 4.9l inline six i've checked the tps cleaned the iac valve and egr valve

 

Well, you have a TPS error code, that is most likely setting the 998 Code.
You can check voltage & resistance on your current TPS or you can replace it.

 

I'll have to do that i found the gasket on the throttle body gasket was trashed