the k&n kit will include a new airbox lid as the stocker wont fit with the K&N filter, without some modding to it, like cutting out some excess plastic underneath

 

Correct:
I run with the stock lid.
I pair of needle nose pliers to remove a few raised ridges that interfer with
the K&N filter...

 

Yeah, I ran eibachs on my '10 G5 gt sedan a few years back and it felt horrible, it just felt loose compared to stock even. Considered buying some cheap for my ss, bought yyz's instead and couldn't be happier

 

If you were to get a good bolt on turbo, the stock downpipe would be restrictive, I even found gains with my old k04 going to 3" catless. Factory charge pipes do fine, except the hot side can be sketchy at 24psi, same with the plastic IC endtanks. I did notice less flex in the pipes when I switched to werks and the heats soak problem was completely resolved with a bigger intercooler. K&n is best unless you're going to a bolt on upgrade turbo, anything bigger than bolt on and you'll have to get an intake made. I'm aiming for mid 11's next spring. My cars coming back from the dyno/Matt howe's within the next few weeks

 

Agreed, the stock DP would be more restrictive than a 3" catless DP.
But, I was referring to a stock DP with a 'cored' 2nd cat, which is better than a 3" catless DP.
Coring the 2nd cat is so easy, & retains off idle low-end torque on the street,
& passes emission inspection, & makes the same power at the track, as a 3" catless DP.

I also agree the a bigger turbo, is a 'game' changer, & requires a different approach to most everything, including a new beefed 4t45e...

 

Backpressure isn't really needed on a turbo'd car for low end torque (in fact, low end torque is increased as spool time is decreased), think of turbo'd racecars running exhaust and dump tube straight out the fender. But for the most part, you're right. The ZZP downpipe isn't really worth it if you have bigger plans for the car. Instant torque, heat and low maintenance is what will kill the trans. A properly sized turbo (k04 is way too small for the LNF for max performance and drivability) should be easier on the transmission than the k04 because it won't be as snappy. I don't plan on building mine right away (money's tight right now) but when I do, I'm going to swap the diff to 3.91 from a base model g6, put in the team green LSD and get a 3200 stall 8" diameter HD torque converter. I'm assuming it'll be fine for a while though. The 4T45e is a beast of a transmission

 

There is a thin line between good/bad backpressure...
A very small amount of backpressure loads the turbo quicker and therefore makes it spool quicker.
I have tried many different DP setups, & the stock 1st cat is perfect for stabilizing the intake/exhaust balance for maximum off idle throttle response, without hurting maximun power output of our stock K04.
https://www.chevyhhr.net/forums/hhr-...t-power-43170/
It's just something that you have to experience, to understand. I swapped, & re-swapped out many DPs to find out that a stock DP, with a 'cored' 2nd cat, is best.

Our K04 is perfectly sized for most excellent performance/driveabillity.
For max performance, of course, a turbo swap, will do the job, at the expense of the most excellent DD street manners of the stock K04.

With simple 'tuning', I can easily 'stall' the stock convertor at 3,000RPM, at the 'tree', & I boost-launch best at 2,500RPM
With every run now, my 60' times are 1.7s, & the stock 4t45e is holding up well.
Why it can do this run after run, I do not know...
I did a little research, & haven't heard anything bad about it, & I've read many horror stories about the supposedly stronger 4t65e ??

I'm really happy with the few mods needed to run low 12s, & at the same time, improving, it to be a better DD on the street...

With just the addition of a 6158 ZZR turbo, I could be in the 11s at the track, & smoke the tires at 60MPH on the street, but the stock 4t45e would '****-the-bed',

I think that you are making the right 'moves', to make a most excellent mid 11 second beast, that will scare the pants off of lot of modified V8 'muscle' cars...

 

After reading this thread I guess I wasted my money on a Trifecta tune and should have gone with the HP and 3 bar set up. Or could I install the 3 bar sensors and "retune" my tune? I do have the option to do that.

 

NOT REALLY...
Why would you say that, how does your buggy run with this tune ??

 

It runs much better than stock, I do get 24 PSI of boost. I have yet to core the second cat, but do have the TTR upper mount and the K&N intake pipe only. I'm using my stock OEM AC/Delco air filter.
As to the filter, I've read some articles that say the stock element is just as good as using the K&N.
Why I say to use the HP tune is, you yourself can change parameters vs Trifecta where you have to rely on a download and give it back to Trifecta to modify.
As far as coring the cat, it's recommended to go 2 3/4". I only have the option at my shop to use 2 1/2" or 3" pipe. Have not taken the exhaust apart to see if a 3" pipe will work but the system is 2 1/2" and see no problem with coring it 2 1/2".
Correct me if I'm wrong on this.