possible blown Head Gasket

[Krem]

without even hearing any of the other symptoms, misfiring cylinders would still point me to timing... but that will prob be addressed once you start lookin under the hood, since you are going to check plugs first...

[cre]

Have you checked for diagnostic codes?
http://www.cygnusx1.net/Supra/TechTi...ror_codes.aspx

The grey coolant is NOT a good sign and it is something I would personally freak out about (there's little that freaks me out). If it is due to mixed coolant the system should be thoroughly flushed (chemical flush, not just water and a light detergent) and most types of coolant do NOT play nicely with each other (some even turn to gelatin on the walls of every surface inside to coolant system and just because it didn't all emulsify it doesn't mean none of it did).

I was asking if it was a GE or GTE due to your question about upgrades.

Originally Posted by 2Fast2Furious

ARP head studs and a 2mm thick piece from HKS and fitted with 1mm oversized valves, and stock cams fitted with AEM cam gears. (lol, not sure what this is all about but if its good I will pay)

The head gasket would have to be changed when you install new head bolts or head studs (either would be fine and ARP is the manufacturer of choice for these fasteners).

A 2mm head gasket is only needed if you are planning on adding a much larger turbo OR if the block and head require significant milling. A thicker head gasket lowers cylinder compression which on a stock engine is unnessecary and will result in a decrease in power. The decrease in compression does allow for you to run a larger boost pressure though which can more than make up for the offset in base power. In a high horsepower build you would still (in an ideal situation, anyway) go with the thinnest head gasket allowable and use different pistons to reduce the compression ratio.

The stock valves flow plenty... especially if combined with a cam of a more aggressive profile. I would upgrade the cams before upgrading the valves. I would get the head rebuilt including a 5 ange valve job (a 3 angle valve job is more than enough, but if you want to go all out I'd go with the 5, it flows even better).

Adjustable cam gears don't always result in a power increase... they are used to tune the power curve to match your needs. They move some torque from one place in the curve to another. You could say they make more power in some cases as they may remove power from one area and add it to another, but it is all trade-off.

Originally Posted by 2Fast2Furious

* there is a smell from under hood, I thought it was oil, I can't destingish if its the sweet coolant smell

If there is a smell, there is a leak... period.

Originally Posted by 2Fast2Furious

* some white smoke from exhaust

Unless the smoke is black, it's oil or coolant (neither is generally a good sign).

Originally Posted by 2Fast2Furious

If I do need new Head Gasket should I just go for stock part? Are they aluminium?

The stock head gasket is a composite graphite material with copper jackets.

There is nothing wrong with using a stock HG on a relatively stock system. The head gasket was never really the problem to begin with nor were the stock head bolts to be blamed; the torque level used on the head bolts was the problem... but then keep in mind that the stockers generally lasted ~20 years on the low torque level. Personally, I'd feel safe on a stock head gasket as long as VERY little material was removed from the head and block deck during the replacement at low boost levels. If you're going to be increasing the boost I'd go with a thicker gasket in which case a metal head gasket and the additional prep work are a requisite.