Let me see if I can explain this another way.
You want to take a front mount intercooler off a Ford Powerstroke diesel and put it in your GN. It passed emissions in the Ford, so you're good, right? NO.
The EPA says you can't tamper with any emissions certified device, which would include things like the engine. The EPA considers the intercooler as part of the engine unit since it was part of that engine in say, an 87 GN, when it was originally certified.
So you still think it will pass? Maybe your local and state sniffer tests, but they aren't run by the EPA. The EPA would have authority, under this new rule, to fine you because you altered (ie: tampered with) your GN's original certified configuration.
So you think you can get it certified? Ok, how? Does the EPA provide this service for free? If not, who provides this service and will they do it for free? If not for free, how much is it going to cost you? The EPA's own website says doing some things with certified vehicles is permitted, but only if re-certified, and they admit this would be cost-prohibitive.
So say a company wants to make downpipes for a GN. Under this new rule, they would not be able to legally sell them for the GN unless they got their product certified. How much does this certification cost? Can a company actually sell a limited quantity (say less than 200) downpipes, pay for the cert, and still turn a profit?
How about an ECM tune? The proposed EPA regs are clear: absolutely NO tampering with an emissions control device. Guess we can't use the stock ECM then. Just go buy an aftermarket ECU and throw it in your GN, right? WRONG. What aftermarket ECU has EPA certification? Is there any way possible an aftermarket ECU could possibly get certification, especially if they could be altered by the end user to produce higher emissions if a mistake was made in the tune? I don't think so.
Let me see if I can explain it another way ... if it looks stock and you cant tell .. does it matter if it passes or not ? .. they wont put you on a sniffer anymore .. PERIOD those days are over !
front mount intercooler .. its EXEMPT chief ! look into the laws carefully ..
you keep using the work TAMPER .. WTF does that mean ?
IF I plug my EGR from the inside of the intake , or plug my turbo breather inlet , or use a stock appearing FPR, or port my heads , or run a TA49 .. WHO IS GOING TO KNOW !!!
there are a lot of parts that have already been exempted from recertification ..
it does not cost that much to certify a part .. but it depends on the part as well.
Downpipes wouldn't be a big deal at all....
The only one that would be an issue would be a Exhaust system as it would have to have a CAT on it ... but you can make it a 2 part exhaust with the CAT being a bolt on part from the downpipe to the CAT back .. guess what .. TEST pipe or FAKE CAT !
Chips .. or tune .. do you really think the EPA "AGENTS" are going to run a binary compare on chips ?? Seriously ??
if you really think the system can't be beat .. your very naïve .