I'd check for bent conrods, using a straw, plastic stick or similar, down the spark plug holes.

Ok so Ive got my new compression tester and got some new results Cylinder 1: 90 psi Cylinder 2: 90 psi Cylinder 3: 50 psi Cylinder 4: 55 psi Cylinder 5: 30 psi Cylinder 6: 25 psi I'm thinking bent con rods at this point but I'll do a leak down test before I start the autopsy. Got any other thoughts on what I should do before I crack the head off?

I use Delta 40's, not 44's. 44's are race mufflers, whereas the 40 is quieter. I have the 3" resonator/Delta 40 2 chamber combo on my F truck and it's quiet enough to be ignored on the street.

all I know is flowmaster super 44s were deafening on BGDAV's 408, and ended up with a spiral flow in the tail pipe additionally and still got the cops telling him he should put it off the road on the spot.    replaced with a pair of the switched mufflers that are super restrictive when closed, but gets it away from the house or through cops without too much attention. 

All depends on what I'm setting up a Clevo for.   Mild street: Tri Y Headers to 2 1/2" Y pipe to 3" collector, 3" x 12" hotdog (with perforated internal tube, not louvers) for front resonator and Flowmaster Delta 40 3" muffler with 3" tail pipe.   Hot street/ drag: Tri Y headers with larger secondary pipes (min. 2 1/4" or even 2 1/2" to dual 3" to 12" x 3" hotdog resonators and dual 3" Flowmasters with dumps. A 2 1/2" balance pipe just before the resonators.  

Thanks Dave, those vids will be handy.

Will be doing that next. I'm guessing maybe something moved out of place when I was installing the pump and hopefully, not me creating an extra problem.

https://www.ebay.com.au/itm/176693782359?_skw=hooker+21502+mufflers&epid=2290978363&itmmeta=01JKH9JE4VA9VX7CGAWDBNSK89&hash=item2923c52757:g:1SQAAOSwBKVnSE9w&itmprp=enc%3AAQAJAAAA0HoV3kP08IDx%2BKZ9MfhVJKnJyYbj6qdmAE3Q7u9smjGJzL5Eic2xY5waf8xJrKGKCQ7doUEBbnztxvQE0ibUSpbyN3rdg5SipWkremV7sSBup1Q7h6CtHe4FeIrU3HSpVuBbr1Qv1XOh%2FSdCG1QEGanjflLkF%2FU%2BORvY8Wh0gqa6Tb8FPRqP7Uygbd3yS%2B3BK8KXIRfIFDvOt2yZAAIfv05xiPfFdnWAZjxd0pkg0x4KK9%2FHMTw8wUNVehKNlM%2BObTa7iNuLyWJihCORVd9gOlA%3D|tkp%3ABk9SR8jiyamcZQ     Just curious about the type/brand of mufflers people are running on their Cleveland's also would you guys recommend the Hooker aero chamber 21502?

At this point , since issues are presenting in both forward & reverse , really need a pressure gauge on there now see what is going on.   Shame you're so far away i'd take a look at it    It's got a ton of oil in it . Usually a deep pan and smaller converter is around 8-8.5 litres