A little info.
Its a swapped L67 Lumina
It has the following:
4" intake
Stage 2 zzp i/c
42# inyectors
Togs headers
3" exhaust
intense Stage 1 blower cam

So I took some time off work to do the i/c
I did. Car ran good. no wot runs considering no tune. Half throttle was fast, very resposive and strong.
After the second day. It started to go bad.

Symptoms
-car would go to 1500-2000 RPMs on its own.
-it would shift to 2nd after reaching 3800 RPMs.
-fuel gauge goes to full then back to empty.
-tried to go half throttle with a no go. Even full throttle doesnt run good. It feels like it loses voltaje.
-alternator went bad. Replaced it. Still does the same thing. Replaced it Sunday. Used the car only today and now its not charging again.

Codes:
P1635
P0300
P0118

Any help?