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Check the valve springs, its possible that they could be floating or or doing something weird when under boost as boost effectively reduces apparent spring pressure. If they are stock, there is a good chance they are weak. Many stock springs fail when used with 1.9 rockers. Also check that the correct retaining plate supplied with the rockers are fitted as the stock ones hit the pushrods and rattle like crazy but they will rattle all of the time blower or not, unlikely but worth looking at.

Also check intake and blower gaskets/seals at they might be leaking and fluttering which makes a buzzing or squealing sound or anything in between.

Thanks for some more idea's vlad01.

I talked my brother into installing his 5% overdriven balancer to his car so I can get a free balancer to try.

I recently removed the lim to port and block off coolant holes and fit a mat sensor, I used sealant on the the lim gaskets and just sealant between lim and charger and torqued to specification have also check for vac leaks.

I installed the rockers with the supplied retainer's from mace i have also checked the push rods for rubbing and straightness all good.

If the rattle is still there after the balancer swap I will look into valve spring replacement thanks.

Yeah the springs are worth looking at. Had them break before after 1.9 rockers were installed. Let us know how you go.

changed the balancer today still has the rattle, going to try the next thing on the list valve springs.

Change the valve spring's today and put the standard pushrods rockers and cradles to eliminate the mace rockers and it still rattles.

Balance shaft bearing maybe or lean backfiring into the inlet

delcowizzid wrote:Balance shaft bearing maybe or lean backfiring into the inlet

Balance shaft has been disabled, wideband AFR reads 10.0 thanks.

Probably not what you want to hear, but I’ve heard a couple like this that have turned out to be cracked or damaged piston lands. Symptoms were very similar to what you’re describing.

Would that only rattle when boosting, because I can remove the supercharger belt and rev to 6000rpm and it doesn't rattle at all while driving.

I know its a bit late but I have heard people having clearance issues when fitting double row timing chains on ecotecs. This is one of them I have read on one site.

You may also encounter clearance issues with the double roller where it will foul and rub on the oil pump housing. One way is to machine down/surface grind your oil pump housing plate approx 0.070" from memory or use 2 'GM' timing cover gaskets to space it out a little.