Sorry buddy, but you need to get a life over rules and regulations. The insurance is covering precieved risks, and you just have to treat your mods like a Group A homologation, and use the best factory parts, and cover off each modification separtely.
I did a search of the 1980 to 1989 Holdens. Most of the modifications, accroding to the letter of the law, were blatant cheats. The dual exahst system was illegal after 1984, but was often fitted after the car left Holden. The emission calibration of Wade 169 cammed VK Director and Group A were also illegal. So were the headers. The mods were covered only by HDT and latterly, Tom Walkinshaw and HSV's intellegence with the emissions rigs. A perfect example is that done by HSV when the last VN Group A was made.
1. FISA banned full race headers, as each car had to race with the stock exhast before the tailpipe flange. The Holden boys just grabed a stock header, made up 8 flanges, and cut back the exhast header length so a brilliant race exhast could run the full length of the car.
2. The second throttle body was unused on the VL and VN Group A, but was able to be used in race form for incrased air flow.
Taken together, these two mods in the VN Commodore pushed the envelope FROM 180 kW to 215kW at 5250 rpm. It varied slightly from the earlier VL Group A motor with 8000 rpm rods, but as a race engine, it was well over 75 hp stronger.
I'm the first to be up front with the mods, but for heavens sake, you are being foolish to abide by the letter of the law...its for fools.
I got my XE certified when I didn't have to because I wanted no problems if some idiot ran into my car when my wife was driving.
My advice is to go for extracors and a replacement exhast that is stock. The XE 4.1 EFI, 4.9 and 5.8 tail pipe were the same, and quite large. Why not just go for the largest stock replacement tail pipe, add the headers/extractors, and shift the air boc to suit the LP Gas mixer. The LP Certificate covers the LPG mods, so that's two mods within the rules
I am not amused by the desire we antipodean Prisoners of Mother England have to ardently follow a stupid ruling the the nth degree. The ruel is there only to stop the baddies. Why 90% of the population should suffer such restriction because 10% wants to see if they can get away with it is beyound me.
Legalisim, a disease I dispise with a passion because it newters peoples hope.
1. Weld the biggest stock replacement 51 mm exhast to the headers, one part.
2. Then the air box gets in the way, so you end up having to move the air box and air meter, which could be an LP Gas modification. Follow Luke Nukems method, but use hard LPG grade heating and ventilation PVC to relocate the air meter, and moutn the LPG mixer above the headers. The LPG certiicate covers that modification
3. Smokey Yunick, David Vizard all taught us all how to work within the rulebook, but still adress the need for performance, so come on. That's the only reason why why rules should exist, so that they curb wrong doing which hurts
a) us
or
b) other people.
Everytime a rule is made, it must be tested. If the rule caves in becasue it is not specific enough, then alternative rulings need to be looked at.
That's why the NASCAR rule book was very different every year from 1949 to up to about 1982, and then it became locked into very specific modifications
There is more than one way to skin a cat.
