I copied pasted this off of another forum
This should be a quick down and dirty to the ever present question. When can I run a 3.4, 3.25, 3.0 etc.... Take into account this write up will be on the more conservative side and I think everyone will agree that this aplies to 95% of GTP'*. Obviously that 5% applies to people with already hurt motors or if you have 150k miles, have gone 10'* of thousands of miles between oil changes etc... you may want to rethink modding at all and start fresh. With this list you should be knock free, however its always a good idea to either buy a scantool or join one of your local chapters and find someone close by with one to scan for kr, however like I said this list is designed to almost guarntee 0 KR.Anyone please feel free to addin suggestions or comments and I will adjust this accordingly.
Well start with the 3.4 pulley as it usually starts the majority of these questions. Below you will find a list of supporting mods that should be in place prior to installing that 3.4. Can you get away with less? Possibly. Have people gotten away with less? Yes. Do you want to take the chance? Enough said.
1. PCM- standard v 1.0 will suffice at this level.
2. CAI/FWI- Cold Air Intake/ Fenderwell Intake, you can build your own or purchase one from a vendor.
3. Ported Exhaust Manifolds/ Headers/ ZZP Powerlog- your choice, at this level Pems or the Powerlog are fine, if your planning on further modding later you will need headers, only you know your budget.
4. 3" Downpipe- Crushbendt which most exhaust shops will do is unadvised, preferable to purchase an aftermarket from one of the vendors.
5. 1-2 Heat range colder plugs. i.e Autolite 104'* or equivelent gapped in the .050-.055 range
6. Ubend delete- just after the cat, most exhaust shops will be able to remove this and put in a straight pipe.
Thats it, doesnt sound too hard right? Fortunatly your reading this, back when alot of us blew our motors there was no such write up and no such guidance. These 5 items are considered necissary, of course you can change your thermo to a 180 unit, also wouldnt hurt. Also quite a few people add a set of 1.9 ratio rockers to that list. If you plan on staying at this mod level, I agree, add the rockers, if your planning on continuing on in the quest of more speed and wont be at this level for very long skip the rockers.
Now onto the 3.2-3.25 Pulley. Obviously this is going to take more extensive supporting mods. Add all from above and include:
1. Camshaft- take your personnal pick, do a search these have been compared time and time again. Addin supporting components, i.e stiffer springs, new pushrods, check with the vendor for individual needs.
2. Ported and Polished heads, larger valves- check with the vendors on this one, will be your best bet to invest in a stage 2 or 3.
3. Headers- if you had Pems before your dangerously close to being out of their level, sell and get some headers.
4. Larger Throttle Body- again these have been compared, take your personnal pick.
5. 2-3 heat range cooler plugs, you can stay with 104'* but may need to switch to 103'*
6. Retuned PCM to add in the cam and free flowing heads etc....
3.0 Pulley needs extensive mods, and honestly you shouldnt even be considering if you have to read this, but just in case take all from above and add:
1. High flow Cat
3. 42.5# injectors
4. Upgraded fuel system
5. Stage 4 heads
6.Powertuner/HPTuners or some other means to custom write onto your PCM during a dyno session.
Now yes notice I didnt say anything about Intercoolers in any of those combinations. Either a Short Stack or Full size intercooler obviously adjusts those combinations. However I dont agree with the idea of just slapping on an IC to address an issue. Can you run a 3.25 with a full size IC and no other supporting mods? Our vendors say yes. Will you get knock? No probably not. Is it a knucleheaded way of thinking? Abso***inglutely. Go ask people who have dealt with forced induction far longer than our motors have been around, if they would almost double the stock boost with just an IC backing it up, not a single one will say yes, Ill bet my next year salary on it. IC'* are great, and have their uses, but you need to have a foundation first. Endeth the sermon.