For the most part- yes octane booster is junk. I do believe Torco has a concentrate- but if you need higher octane than premium to keep your car from knocking- then you need to run less boost or adjust timing in your pcm.

Some injector cleaners are ok- but you have to be careful as there are a lot of gimmicky 'tricks in a bottle' of various cleaners and such that do little to nothing for your engine (as you've probably seen the local parts store has a whole section of 'engine restorers', 'engine cleaners', and so on.

The LS4 is not a flex fuel engine. Owners manual does not say it can run E85, nor does the gas cap. Which means, you'd likely need much larger injectors to be able to run E85 on the LS4.

 

ok, what about fuel injector cleaners? are they any good?

 

seafoam comes to mind for me. i've used it dozens of times on my cars, atvs, snowmobiles, lawn mowers, etc. there is GM brand of injector cleaner that i've heard of but can't remember the name right now. i'm sure someone will chime in.


as for the 5.3L being a flex fuel vehicle, the LS4s are not, but some of the 5.3 truck engines are in the chevy 1/2 tons. not sure about the 6.0L in the 3/4 tons?? i don't think a flex fuel option is offered.

 

The only engine offered in the Monte's that is Flex-Fuel is the 3500. The 3900 and 5.3L offered in the Monte were never Flex-Fuel.

I think in 2007 they started offering the 3900 as a Flex-Fuel, along with the Active Fuel Management. But this was only available in the Impala since they dropped the 3900 in the Monte.

 

I've used the RedLine Complete Fuel System cleaner with good results.