What are good things to add and how often? I added some fuel system and injector cleaner and damn I felt the difference.

 

its all in your head. Additives are almost always pointless and dont do anything.

 

that's not necessarily true... i added fuel injector cleaner to my car and there was definitely a difference in the way it drove. i've been adding it since. i would stay away from oil additives, theres a whole write-up around here somewhere as to why, but it'll wind up screwing you up more than anything

 

Big no no for oil additives, you should use fuel injector cleaner like every 30k. It'll help carbon build up in the valves and such. The best thing is to run a cleaner through the intake to help get rid of carbon. Just make sure what you doing when you run it through the intake.

 

TE, When I bought the additive i thought the same thing. but my mpg improved and it idles better. Also it feels like its smoother when i take it to 5k

 

You can also use Octane Boosters to raise your octane level for the more modified engines. But you have to put it in like every tank.

 

I've seen and heard of that but what does the octane booster do?

 

no not really... i've added it to my rs cause i found some around the house and i didnt notice a difference

 

i know in turbo cars they run alot better a higher octane. i just have the "basic" mods on a 98 gst. (i'e) mbc and thats about all. and 15psi and i feel a good bit of difference, engine runs smoother and less engine noise.

 

Well many additives are not recommended cause they do more harm than good. However, my lifters were ticking on my 97 Gst, so I dumped a bottle of Lucas Pure Synthetic Stabilizer in my oil and its never happend since.