Which Gen 6 modification provides the most HP/$?
 

Mods are dealt with everyday here, but I don't recall see a ranking of mods based on cost and HP gained.

I suppose technically you would have to dyno with each mod to say for certain, but we know that mods such as headers would be near the top of the ranking.

Headers has to be up there on the list. I think the bottleneck in the stock manifolds is the biggest impediment to power. Tune is pretty important in that regard also.

And I guess a 2650R is the ultimate bolt on LOL.

For initial cost...biggest gain for the dollar would be Nitrous. Cost is less than many axle back exhaust systems. Over the long run it could start to even itself out with other mods depending how many bottles you go through.

I gained 150 going to the Maggie 2650

Nothing is cheap on these cars. For a forced induction vehicle though, typically increasing boost is the most cost effective HP mod which means a pulley swap, however because the stock exhaust manifolds are so restrictive on these cars, headers pretty much become necessary when increasing the boost. Headers are not cheap, nor is installation if you pay someone to do it and then you must also have the PCM tuned which adds more cost. The way these cars are designed, its almost like there are no cheap effective HP mods without some expensive supporting mod to go with it. Even after you go full bolt on, then you have to go into the engine to add a cam for more fuel, even if you didn't want a cam, it becomes a necessity to continue to increase power.

Just day dreaming here..........if you bought a Maggie 2650, paid to have it installed and a custom tune. The sold the stock blower for a reasonable amount.
How much do you think you would have invested?

E85.

That's a good point, which does require a tune and flex fuel sensor also though. Nonetheless, probably the cheapest bang for the buck mod if you plan to do nothing else and you have E85 readily available and don't mind calculating your blend and the 25-30% reduction in gas mileage.

Yes. Excellent HP to $$ ratio.

If I were to start with a stock car first mods would be the following:

Rotofab
2" headers/ORX
Flex fuel sensor

Those three will get you to 625-650 depending on dyno on an E blend. Pulley on stock fuel system limits your ability to run E and these cars see big gains from just E50. Also no heat issues because you're at stock boost levels. Simple and reliable.

The lower price point of E85 negates the reduction in fuel mileage. The cost of operation is still lower then 93 pump gas.

Prices vary depending on your location. I've done it in my Hellcat for 3 years, it comes up close to the same in my area but costs JUST slightly more to run E85 than 93 but you will also make more trips to the pump which can be a nuisance but was worth it for cheap race gas. I'm all for E85 though. The other part of it is that if you're traveling, you may not be able to find E85, so you'll be down on power using 93.

My builder says I need both a high and low side FP to run E85. I mention this only because there's always more work/cost to a mod than one might think.

The 2650 makes a great example:

It'll cost say $8100 delivered, and IF you know how to remove the Eaton and install the Maggie, and make NO other mods other than a tune, KaTech says it would likely make around 600-620 wheel, which is 35-55 hp more than mine stock. But, of course, I would and you would make other mods costing $$$$$.

Which reminds me, how much more power will a stock LT4 make with only a tune? Perhaps this is the most cost effective mod?

I have been running E85 since 2017. The pros outweigh the cons.

I made my statement based on coming from a stock ZL1. You didn't specify what prerequisites the recommendations should be based on. Yes for you to run E85 there is more cost involved. For a stock ZL1 you need a flex sensor and tune to run E70. That will need a 50-70whp gain. The car will also run more consistent all around pull after pull. No other mod will gain that for the cost.